diff --git a/.verify-helper/timestamps.remote.json b/.verify-helper/timestamps.remote.json
index b41026b77..c8da6b3aa 100644
--- a/.verify-helper/timestamps.remote.json
+++ b/.verify-helper/timestamps.remote.json
@@ -20,8 +20,6 @@
 "tests/library_checker_aizu_tests/data_structures/distinct_query.test.cpp": "2026-01-18 11:15:41 +0000",
 "tests/library_checker_aizu_tests/data_structures/dsu.test.cpp": "2026-01-22 10:08:22 -0700",
 "tests/library_checker_aizu_tests/data_structures/dsu_bipartite.test.cpp": "2026-01-18 02:20:40 +0000",
-"tests/library_checker_aizu_tests/data_structures/dsu_restorable.test.cpp": "2026-01-18 02:20:40 +0000",
-"tests/library_checker_aizu_tests/data_structures/dsu_segtree_undo_trick.test.cpp": "2026-01-23 04:31:29 +0000",
 "tests/library_checker_aizu_tests/data_structures/implicit_seg_tree.test.cpp": "2026-01-18 11:15:41 +0000",
 "tests/library_checker_aizu_tests/data_structures/kd_bit_1d.test.cpp": "2026-02-19 18:06:52 -0700",
 "tests/library_checker_aizu_tests/data_structures/kruskal_tree_aizu.test.cpp": "2026-01-18 02:20:40 +0000",
@@ -39,7 +37,6 @@
 "tests/library_checker_aizu_tests/data_structures/persistent_queue_tree.test.cpp": "2026-01-18 11:15:41 +0000",
 "tests/library_checker_aizu_tests/data_structures/persistent_seg_tree.test.cpp": "2026-01-18 11:15:41 +0000",
 "tests/library_checker_aizu_tests/data_structures/pq_ds_undo_sliding_window.test.cpp": "2026-01-18 02:20:40 +0000",
-"tests/library_checker_aizu_tests/data_structures/pq_ds_undo_with_dsu.test.cpp": "2026-01-18 02:20:40 +0000",
 "tests/library_checker_aizu_tests/data_structures/range_parallel_dsu.test.cpp": "2026-01-22 10:08:22 -0700",
 "tests/library_checker_aizu_tests/data_structures/rmq_linear.test.cpp": "2026-01-18 11:15:41 +0000",
 "tests/library_checker_aizu_tests/data_structures/rmq_sparse_table.test.cpp": "2026-01-18 11:15:41 +0000",
@@ -71,10 +68,9 @@
 "tests/library_checker_aizu_tests/graphs/offline_incremental_scc.test.cpp": "2026-01-22 10:08:22 -0700",
 "tests/library_checker_aizu_tests/graphs/strongly_connected_components_aizu.test.cpp": "2026-01-17 13:05:42 -0700",
 "tests/library_checker_aizu_tests/graphs/strongly_connected_components_lib_checker.test.cpp": "2026-01-17 13:05:42 -0700",
-"tests/library_checker_aizu_tests/graphs/two_edge_components.test.cpp": "2026-01-18 02:20:40 +0000",
+"tests/library_checker_aizu_tests/graphs/two_edge_components.test.cpp": "2026-02-27 11:11:58 -0700",
 "tests/library_checker_aizu_tests/handmade_tests/count_paths.test.cpp": "2026-01-18 11:15:41 +0000",
 "tests/library_checker_aizu_tests/handmade_tests/dsu.test.cpp": "2026-01-22 10:08:22 -0700",
-"tests/library_checker_aizu_tests/handmade_tests/dsu_size.test.cpp": "2026-01-18 02:20:40 +0000",
 "tests/library_checker_aizu_tests/handmade_tests/edge_cd_small_trees.test.cpp": "2025-09-07 15:50:55 -0600",
 "tests/library_checker_aizu_tests/handmade_tests/fib_matrix_expo.test.cpp": "2026-01-28 21:48:16 -0700",
 "tests/library_checker_aizu_tests/handmade_tests/functional_graph.test.cpp": "2025-08-06 16:18:37 -0600",
@@ -90,6 +86,7 @@
 "tests/library_checker_aizu_tests/handmade_tests/sa_find_subarray.test.cpp": "2026-01-27 18:11:48 +0000",
 "tests/library_checker_aizu_tests/handmade_tests/seg_tree_find.test.cpp": "2026-01-23 04:31:29 +0000",
 "tests/library_checker_aizu_tests/handmade_tests/seg_tree_find_small.test.cpp": "2026-01-23 04:31:29 +0000",
+"tests/library_checker_aizu_tests/handmade_tests/seg_tree_midpoint.test.cpp": "2026-02-27 11:11:58 -0700",
 "tests/library_checker_aizu_tests/loops/chooses.test.cpp": "2025-02-10 14:50:36 -0700",
 "tests/library_checker_aizu_tests/loops/quotients.test.cpp": "2024-11-17 14:04:03 -0600",
 "tests/library_checker_aizu_tests/loops/submasks.test.cpp": "2025-02-10 14:50:36 -0700",
diff --git a/library/dsu/dsu_restorable.hpp b/library/dsu/dsu_restorable.hpp
deleted file mode 100644
index e06d411da..000000000
--- a/library/dsu/dsu_restorable.hpp
+++ /dev/null
@@ -1,41 +0,0 @@
-#pragma once
-//! https://github.com/ucf-programming-team/hackpack-cpp/blob/master/content/data-structures/DSURestorable.h
-//! DSU without path compression, so non-amortized. Most
-//! operations are O(log n)
-struct dsu_restorable {
-  int num_sets;
-  vi p;
-  vector<ll> subtree;
-  vector<optional<array<int, 3>>> st;
-  dsu_restorable(int n):
-    num_sets(n), p(n, -1), subtree(n) {}
-  int find(int v) {
-    while (p[v] >= 0) v = p[v];
-    return v;
-  }
-  bool join(int u, int v) {
-    st.emplace_back();
-    if ((u = find(u)) == (v = find(v))) return 0;
-    if (p[u] > p[v]) swap(u, v);
-    st.back() = {u, v, p[v]};
-    p[u] += p[v], p[v] = u, subtree[u] += subtree[v],
-                  num_sets--;
-    return 1;
-  }
-  void undo() {
-    if (auto b = st.back()) {
-      auto [u, v, sz_v] = *b;
-      num_sets++, subtree[u] -= subtree[v], p[v] = sz_v,
-                                            p[u] -= p[v];
-    }
-    st.pop_back();
-  }
-  int size(int v) { return -p[find(v)]; }
-  bool same_set(int u, int v) {
-    return find(u) == find(v);
-  }
-  ll sum(int v) { return subtree[find(v)]; }
-  void add(int v, int d) {
-    while (v >= 0) subtree[v] += d, v = p[v];
-  }
-};
diff --git a/tests/library_checker_aizu_tests/data_structures/dsu_restorable.test.cpp b/tests/library_checker_aizu_tests/data_structures/dsu_restorable.test.cpp
deleted file mode 100644
index 2dce308ff..000000000
--- a/tests/library_checker_aizu_tests/data_structures/dsu_restorable.test.cpp
+++ /dev/null
@@ -1,39 +0,0 @@
-#define PROBLEM \
-  "https://judge.yosupo.jp/problem/persistent_unionfind"
-#include "../template.hpp"
-#include "../../../library/dsu/dsu_restorable.hpp"
-int main() {
-  cin.tie(0)->sync_with_stdio(0);
-  int n, q;
-  cin >> n >> q;
-  vector<vector<int>> childs(q + 1), queries(q + 1);
-  vector<int> query_u(q + 1), query_v(q + 1);
-  for (int i = 1; i <= q; i++) {
-    int type, k;
-    cin >> type >> k >> query_u[i] >> query_v[i];
-    k++;
-    if (type == 0) childs[k].push_back(i);
-    else {
-      assert(type == 1);
-      queries[k].push_back(i);
-    }
-  }
-  vector<int> res(q + 1, -1);
-  {
-    dsu_restorable dsu(n);
-    auto dfs = [&](auto&& self, int u) -> void {
-      for (auto idx : queries[u])
-        res[idx] =
-          dsu.same_set(query_u[idx], query_v[idx]);
-      for (auto child : childs[u]) {
-        dsu.join(query_u[child], query_v[child]);
-        self(self, child);
-        dsu.undo();
-      }
-    };
-    dfs(dfs, 0);
-  }
-  for (int i = 1; i <= q; i++)
-    if (res[i] != -1) cout << res[i] << "\n";
-  return 0;
-}
diff --git a/tests/library_checker_aizu_tests/data_structures/dsu_segtree_undo_trick.test.cpp b/tests/library_checker_aizu_tests/data_structures/dsu_segtree_undo_trick.test.cpp
deleted file mode 100644
index f9ea716d8..000000000
--- a/tests/library_checker_aizu_tests/data_structures/dsu_segtree_undo_trick.test.cpp
+++ /dev/null
@@ -1,127 +0,0 @@
-#define PROBLEM \
-  "https://judge.yosupo.jp/problem/dynamic_graph_vertex_add_component_sum"
-#include "../template.hpp"
-#include "../../../library//dsu/dsu_restorable.hpp"
-#include "../../../library/data_structures_[l,r)/lazy_seg_tree.hpp"
-int main() {
-  cin.tie(0)->sync_with_stdio(0);
-  int n, q;
-  cin >> n >> q;
-  dsu_restorable dsu(n);
-  for (int i = 0; i < n; i++) cin >> dsu.subtree[i];
-  vector<vector<pair<int, int>>> tree(2 * q);
-  auto add_edge = [&](auto&& self, int l, int r,
-                    int node_u, int node_v, int tl, int tr,
-                    int v) -> void {
-    if (r <= tl || tr <= l) return;
-    if (l <= tl && tr <= r) {
-      tree[v].emplace_back(node_u, node_v);
-      return;
-    }
-    int tm = split(tl, tr);
-    self(self, l, r, node_u, node_v, tl, tm, 2 * v);
-    self(self, l, r, node_u, node_v, tm, tr, 2 * v + 1);
-  };
-  struct query {
-    int type, v, x;
-  };
-  vector<query> queries(q);
-  {
-    map<pair<int, int>, int> insert_time;
-    for (int i = 0; i < q; i++) {
-      int type;
-      cin >> type;
-      if (type == 0) {
-        int u, v;
-        cin >> u >> v;
-        if (u > v) swap(u, v);
-        assert(!insert_time.contains({u, v}));
-        insert_time[{u, v}] = i;
-      } else if (type == 1) {
-        int u, v;
-        cin >> u >> v;
-        if (u > v) swap(u, v);
-        assert(insert_time.contains({u, v}));
-        add_edge(add_edge, insert_time[{u, v}], i, u, v, 0,
-          q, 1);
-        insert_time.erase({u, v});
-      } else if (type == 2) {
-        int v, x;
-        cin >> v >> x;
-        queries[i] = {2, v, x};
-      } else {
-        assert(type == 3);
-        int v;
-        cin >> v;
-        queries[i] = {3, v, -1};
-      }
-    }
-    for (auto [edge, i_time] : insert_time)
-      add_edge(add_edge, i_time, q, edge.first,
-        edge.second, 0, q, 1);
-  }
-  auto dfs = [&](auto&& self, int tl, int tr,
-               int v) -> void {
-    for (auto [node_u, node_v] : tree[v])
-      dsu.join(node_u, node_v);
-    assert((v >= q) == ((tr - tl) == 1));
-    if (v >= q) { // leaf node
-      const int depth_leaf = __lg(v),
-                max_depth = __lg(2 * q - 1);
-      if (tl == 0) { // left-most leaf
-        assert(v == (1 << max_depth));
-        assert(depth_leaf == max_depth);
-      }
-      assert(q <= v && v < 2 * q);
-      assert(depth_leaf == max_depth ||
-        depth_leaf == max_depth - 1);
-      if ((q & (q - 1)) == 0)
-        assert(depth_leaf == max_depth);
-      if (queries[tl].type == 2)
-        dsu.add(queries[tl].v, queries[tl].x);
-      else if (queries[tl].type == 3)
-        cout << dsu.sum(queries[tl].v) << '\n';
-    } else {
-      assert(1 <= v && v < q);
-      if (((tr - tl) & (tr - tl - 1)) == 0)
-        assert(split(tl, tr) == (tl + tr) / 2);
-      {
-        int pow_2 = 1 << __lg(tr - tl);
-        if (tl + pow_2 < tr - pow_2 / 2) {
-          assert(pow_2 != tr - tl);
-          assert(pow_2 / 2 < tr - tl - pow_2 &&
-            tr - tl - pow_2 < pow_2);
-          assert(pow_2 <= 2 * (tr - tl - pow_2) - 1 &&
-            2 * (tr - tl - pow_2) - 1 < 2 * pow_2 - 1);
-          assert(__lg(pow_2) ==
-              __lg(2 * ((tr - tl) - pow_2) - 1) &&
-            __lg(pow_2) == __lg(2 * pow_2 - 1));
-        } else if (pow_2 < tr - tl) {
-          assert(pow_2 / 2 < tr - tl - pow_2 / 2 &&
-            tr - tl - pow_2 / 2 <= pow_2);
-          assert(
-            pow_2 <= 2 * ((tr - tl) - pow_2 / 2) - 1 &&
-            2 * ((tr - tl) - pow_2 / 2) - 1 <=
-              2 * pow_2 - 1);
-          assert(__lg(2 * (tr - tl - pow_2 / 2) - 1) ==
-            __lg(2 * pow_2 - 1));
-          assert(__lg(2 * ((tr - tl) - pow_2 / 2) - 1) ==
-            __lg(pow_2));
-          assert(
-            __lg(pow_2) == 1 + __lg(2 * (pow_2 / 2) - 1));
-        }
-      }
-      int tm = split(tl, tr);
-      // in particular, this tests that split works with
-      // negatives
-      assert(split(tl - 1234, tr - 1234) == tm - 1234);
-      assert(split(tl - 1, tr - 1) == tm - 1);
-      assert(split(tl + 50, tr + 50) == tm + 50);
-      self(self, tl, tm, 2 * v);
-      self(self, tm, tr, 2 * v + 1);
-    }
-    for (int i = 0; i < sz(tree[v]); i++) dsu.undo();
-  };
-  dfs(dfs, 0, q, 1);
-  return 0;
-}
diff --git a/tests/library_checker_aizu_tests/data_structures/pq_ds_undo_with_dsu.test.cpp b/tests/library_checker_aizu_tests/data_structures/pq_ds_undo_with_dsu.test.cpp
deleted file mode 100644
index 16ed0c123..000000000
--- a/tests/library_checker_aizu_tests/data_structures/pq_ds_undo_with_dsu.test.cpp
+++ /dev/null
@@ -1,77 +0,0 @@
-#define PROBLEM \
-  "https://judge.yosupo.jp/problem/dynamic_graph_vertex_add_component_sum"
-// since _GLIBCXX_DEBUG causes std::map insert/erase
-// operations to be O(n)
-#undef _GLIBCXX_DEBUG
-#include "../template.hpp"
-#include "../../../library/dsu/dsu_restorable.hpp"
-#include "../../../library/data_structures_[l,r)/uncommon/priority_queue_of_updates.hpp"
-int main() {
-  cin.tie(0)->sync_with_stdio(0);
-  int n, q;
-  cin >> n >> q;
-  vector<int> initial_values(n);
-  for (int i = 0; i < n; i++) cin >> initial_values[i];
-  vector<int> time_remove(q, -1);
-  struct query {
-    int type, u, v, x;
-  };
-  vector<query> queries(q);
-  {
-    map<pair<int, int>, int> insert_time;
-    for (int i = 0; i < q; i++) {
-      int type;
-      cin >> type;
-      if (type == 0) {
-        int u, v;
-        cin >> u >> v;
-        if (u > v) swap(u, v);
-        assert(!insert_time.contains({u, v}));
-        insert_time[{u, v}] = i;
-        queries[i] = {type, u, v, -1};
-      } else if (type == 1) {
-        int u, v;
-        cin >> u >> v;
-        if (u > v) swap(u, v);
-        assert(insert_time.contains({u, v}));
-        time_remove[insert_time[{u, v}]] = i;
-        insert_time.erase({u, v});
-        queries[i] = {type, -1, -1, -1};
-      } else if (type == 2) {
-        int v, x;
-        cin >> v >> x;
-        queries[i] = {type, -1, v, x};
-      } else {
-        assert(type == 3);
-        int v;
-        cin >> v;
-        queries[i] = {type, -1, v, -1};
-      }
-    }
-  }
-  dsu_restorable dsu_r(n);
-  pq_updates<dsu_restorable, int, int> pq(dsu_r);
-  for (int i = 0; i < n; i++)
-    pq.ds.add(i, initial_values[i]);
-  int curr_priority_counter = -q;
-  for (int i = 0; i < q; i++) {
-    int type = queries[i].type;
-    if (type == 0) {
-      int u = queries[i].u, v = queries[i].v;
-      int curr_pri;
-      if (time_remove[i] == -1)
-        curr_pri = curr_priority_counter--;
-      else curr_pri = -time_remove[i];
-      pq.push_update(u, v, curr_pri);
-    } else if (type == 1) pq.pop_update();
-    else if (type == 2) {
-      int v = queries[i].v, x = queries[i].x;
-      pq.ds.add(v, x);
-    } else {
-      assert(type == 3);
-      int v = queries[i].v;
-      cout << pq.ds.sum(v) << '\n';
-    }
-  }
-  return 0;
-}
diff --git a/tests/library_checker_aizu_tests/graphs/two_edge_components.test.cpp b/tests/library_checker_aizu_tests/graphs/two_edge_components.test.cpp
index be5f84be0..b2af2ee6b 100644
--- a/tests/library_checker_aizu_tests/graphs/two_edge_components.test.cpp
+++ b/tests/library_checker_aizu_tests/graphs/two_edge_components.test.cpp
@@ -2,7 +2,7 @@
   "https://judge.yosupo.jp/problem/two_edge_connected_components"
 #include "../template.hpp"
 #include "../../../library/graphs/uncommon/bridge_tree.hpp"
-#include "../../../library/dsu/dsu_restorable.hpp"
+#include "../../../library/dsu/dsu.hpp"
 int main() {
   cin.tie(0)->sync_with_stdio(0);
   int n, m;
@@ -33,7 +33,7 @@ int main() {
       accumulate(begin(is_br), end(is_br), 0);
     assert(sum_deg % 2 == 0 && sum_deg / 2 == cnt_bridges);
   }
-  dsu_restorable dsu(n);
+  DSU dsu(n);
   int num_sets_dsu = n;
   for (int i = 0; i < m; i++) {
     if (!is_br[i]) {
@@ -45,12 +45,11 @@ int main() {
   for (int i = 0; i < m; i++) {
     if (is_br[i]) {
       auto [u, v] = edges[i];
-      bool same_set = dsu.same_set(u, v);
-      assert(!same_set);
+      assert(dsu.f(u) != dsu.f(v));
     }
   }
   for (int i = 0; i < n; i++) {
-    int par_of_cc = dsu.find(i);
+    int par_of_cc = dsu.f(i);
     assert(br_id[i] == br_id[par_of_cc]);
   }
   for (int i = 0; i < m; i++) {
diff --git a/tests/library_checker_aizu_tests/handmade_tests/dsu_size.test.cpp b/tests/library_checker_aizu_tests/handmade_tests/dsu_size.test.cpp
deleted file mode 100644
index 3e8b594e3..000000000
--- a/tests/library_checker_aizu_tests/handmade_tests/dsu_size.test.cpp
+++ /dev/null
@@ -1,54 +0,0 @@
-#define PROBLEM \
-  "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ITP1_1_A"
-#include "../template.hpp"
-#include "../../../library/contest/random.hpp"
-#include "../../../library/dsu/dsu_restorable.hpp"
-int main() {
-  cin.tie(0)->sync_with_stdio(0);
-  for (int n = 1; n < 100; n++) {
-    dsu_restorable dsu(n);
-    vector<vector<int>> adj(n);
-    vector<pair<int, int>> edge_st;
-    for (int q = 0; q < 100; q++) {
-      int type = rnd<int>(0, 2);
-      if (type == 0) {
-        int u = rnd<int>(0, n - 1), v = rnd(0, n - 1);
-        dsu.join(u, v);
-        adj[u].push_back(v);
-        adj[v].push_back(u);
-        edge_st.emplace_back(u, v);
-      } else if (type == 1) {
-        vector<vector<int>> comps;
-        vector<bool> vis(n);
-        auto dfs = [&](auto&& self, int node) -> void {
-          comps.back().push_back(node);
-          for (auto next : adj[node])
-            if (!vis[next]) {
-              vis[next] = true;
-              self(self, next);
-            }
-        };
-        for (int i = 0; i < n; i++) {
-          if (!vis[i]) {
-            comps.emplace_back();
-            vis[i] = true;
-            dfs(dfs, i);
-          }
-        }
-        assert(sz(comps) == dsu.num_sets);
-        for (auto& cc : comps)
-          for (auto node : cc)
-            assert(dsu.size(node) == sz(cc));
-      } else if (!empty(edge_st)) {
-        auto [u, v] = edge_st.back();
-        edge_st.pop_back();
-        assert(adj[u].back() == v && adj[v].back() == u);
-        adj[u].pop_back();
-        adj[v].pop_back();
-        dsu.undo();
-      }
-    }
-  }
-  cout << "Hello World\n";
-  return 0;
-}
diff --git a/tests/library_checker_aizu_tests/handmade_tests/seg_tree_midpoint.test.cpp b/tests/library_checker_aizu_tests/handmade_tests/seg_tree_midpoint.test.cpp
new file mode 100644
index 000000000..7f3d84bdf
--- /dev/null
+++ b/tests/library_checker_aizu_tests/handmade_tests/seg_tree_midpoint.test.cpp
@@ -0,0 +1,67 @@
+#define PROBLEM \
+  "https://onlinejudge.u-aizu.ac.jp/problems/ITP1_1_A"
+#include "../template.hpp"
+#include "../../../library/data_structures_[l,r)/seg_tree_midpoint.hpp"
+int main() {
+  cin.tie(0)->sync_with_stdio(0);
+  for (int n = 1; n < 5000; n++) {
+    auto dfs = [&](auto&& self, int tl, int tr,
+                 int v) -> void {
+      assert((v >= n) == ((tr - tl) == 1));
+      if (v >= n) { // leaf node
+        const int depth_leaf = __lg(v),
+                  max_depth = __lg(2 * n - 1);
+        if (tl == 0) { // left-most leaf
+          assert(v == (1 << max_depth));
+          assert(depth_leaf == max_depth);
+        }
+        assert(n <= v && v < 2 * n);
+        assert(depth_leaf == max_depth ||
+          depth_leaf == max_depth - 1);
+        if ((n & (n - 1)) == 0)
+          assert(depth_leaf == max_depth);
+      } else {
+        assert(1 <= v && v < n);
+        if (((tr - tl) & (tr - tl - 1)) == 0)
+          assert(split(tl, tr) == (tl + tr) / 2);
+        {
+          int pow_2 = 1 << __lg(tr - tl);
+          if (tl + pow_2 < tr - pow_2 / 2) {
+            assert(pow_2 != tr - tl);
+            assert(pow_2 / 2 < tr - tl - pow_2 &&
+              tr - tl - pow_2 < pow_2);
+            assert(pow_2 <= 2 * (tr - tl - pow_2) - 1 &&
+              2 * (tr - tl - pow_2) - 1 < 2 * pow_2 - 1);
+            assert(__lg(pow_2) ==
+                __lg(2 * ((tr - tl) - pow_2) - 1) &&
+              __lg(pow_2) == __lg(2 * pow_2 - 1));
+          } else if (pow_2 < tr - tl) {
+            assert(pow_2 / 2 < tr - tl - pow_2 / 2 &&
+              tr - tl - pow_2 / 2 <= pow_2);
+            assert(
+              pow_2 <= 2 * ((tr - tl) - pow_2 / 2) - 1 &&
+              2 * ((tr - tl) - pow_2 / 2) - 1 <=
+                2 * pow_2 - 1);
+            assert(__lg(2 * (tr - tl - pow_2 / 2) - 1) ==
+              __lg(2 * pow_2 - 1));
+            assert(__lg(2 * ((tr - tl) - pow_2 / 2) - 1) ==
+              __lg(pow_2));
+            assert(__lg(pow_2) ==
+              1 + __lg(2 * (pow_2 / 2) - 1));
+          }
+        }
+        int tm = split(tl, tr);
+        // in particular, this tests that split works with
+        // negatives
+        assert(split(tl - 1234, tr - 1234) == tm - 1234);
+        assert(split(tl - 1, tr - 1) == tm - 1);
+        assert(split(tl + 50, tr + 50) == tm + 50);
+        self(self, tl, tm, 2 * v);
+        self(self, tm, tr, 2 * v + 1);
+      }
+    };
+    dfs(dfs, 0, n, 1);
+  }
+  cout << "Hello World\n";
+  return 0;
+}