func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, m, k, a[300000][2], fa[300000], sz[300000], top[300000], d[300000],       prf[300000], f1[300000], q1[300000], q2[300000];   vector<int> g[300000], b[300000];   map<int, map<int, int> > f2[300000];   long long ans;   void dfs1(int u) {     d[u] = d[fa[u]] + 1;     sz[u] = 1;     for (int v : g[u])       if (v != fa[u]) {         fa[v] = u;         dfs1(v);         sz[u] += sz[v];       }   }   void dfs2(int u) {     if (!top[u]) top[u] = u;     b[top[u]].push_back(u);     int t = 0;     for (int v : g[u])       if (v != fa[u] && sz[v] > sz[t]) t = v;     if (!t) return;     prf[u] = t;     top[t] = top[u];     dfs2(t);     for (int v : g[u])       if (v != fa[u] && v != t) dfs2(v);   }   int lca(int x, int y) {     for (; top[x] != top[y]; x = fa[top[x]])       if (d[top[x]] < d[top[y]]) swap(x, y);     return d[x] < d[y] ? x : y;   }   int go(int x, int k) {     int len = d[x] - d[top[x]];     if (len < k) return go(fa[top[x]], k - len - 1);     return b[top[x]][len - k];   }   int add1(int x, int y) {     int len = d[x] - d[y];     if (len < k) return x;     int z = go(x, len - k + 1);     ++f1[x];     --f1[z];     return z;   }   void add2(int u1, int u2, int v1, int v2) {     if (top[u1] > top[v1]) swap(u1, v1), swap(u2, v2);     if (d[u1] > d[u2]) swap(u1, u2);     ++f2[top[u1]][top[v1]][d[u1]];     --f2[top[u1]][top[v1]][d[u2] + 1];   }   void add(int x, int y) {     int z = lca(x, y);     x = add1(x, z);     y = add1(y, z);     int u = x, v = y;     int n1 = 0, n2 = 0;     for (; top[u] != top[z]; u = fa[top[u]]) q1[++n1] = u;     for (; top[v] != top[z]; v = fa[top[v]]) q2[++n2] = v;     if (u != z) q1[++n1] = u;     if (v != z) q2[++n2] = v;     for (int i1 = 1, i2 = n2; i1 <= n1; ++i1) {       int u1 = q1[i1], u2 = top[u1];       if (d[u2] <= d[z]) u2 = prf[z];       for (; i2; --i2) {         int v1 = q2[i2], v2 = top[v1];         if (d[v2] <= d[z]) v2 = prf[z];         if (d[u1] + d[v1] - d[z] * 2 < k) continue;         int len = d[u1] + d[v1] - d[z] * 2;         int w1 = go(v1, len - k), w2 = 0;         len = d[u2] + d[v1] - d[z] * 2;         if (len >= k) {           w2 = go(v1, len - k);           add2(u1, u2, w1, w2);           break;         }         len = d[u1] + d[v1] - d[z] * 2;         w2 = go(u1, len - k);         add2(u1, w2, w1, v1);         u1 = fa[w2];       }     }   }   long long C(long long x) { return x * (x - 1) / 2; }   void dfs3(int u, int t) {     for (int v : g[u])       if (v != fa[u]) {         dfs3(v, t);         f1[u] += f1[v];       }     ans += C(f1[u]) * t;   }   void calc(int t) {     for (int i = 1; i <= n; ++i) {       for (auto j : f2[i]) {         long long sum = 0, lst = 0;         for (auto k : j.second) {           ans += (k.first - lst) * C(sum) * t;           lst = k.first;           sum += k.second;         }       }       f2[i].clear();     }   }   int main() {     scanf( %d%d%d , &n, &m, &k);     for (int i = 1; i < n; ++i) {       int x, y;       scanf( %d%d , &x, &y);       g[x].push_back(y);       g[y].push_back(x);     }     dfs1(1);     dfs2(1);     for (int i = 1; i <= m; ++i) {       scanf( %d%d , a[i] + 0, a[i] + 1);       add(a[i][0], a[i][1]);     }     dfs3(1, 1);     calc(1);     memset(f1, 0, sizeof f1);     ++k;     for (int i = 1; i <= m; ++i) add(a[i][0], a[i][1]);     dfs3(1, -1);     calc(-1);     printf( %lld n , ans);     return 0;   }   