func_code_string: #include <bits/stdc++.h>   using namespace std;   long long const M = 1e5 + 10, mod = 1e9 + 7, inf = 1e9 + 10;   long long par[M][30], dp[M], zt[M], sum[M], val[M][30], sum2[M], n, dp2[M],       len = 0, h[M];   vector<long long> adj[M], edg[M], inc[M];   long long mrg(long long x, long long y, long long sm, long long cnt) {     long long ans = (x + ((y * y) % mod) * cnt + ((sm * y) % mod) * 2) % mod;     return ans;   }   void dfs_down(long long v, long long l, long long c) {     zt[v] = 1;     val[v][0] = c;     h[v] = h[l] + 1;     par[v][0] = l;     for (long long i = 1; i <= 20; i++) {       par[v][i] = par[par[v][i - 1]][i - 1];       val[v][i] = val[par[v][i - 1]][i - 1] + val[v][i - 1];       val[v][i] %= mod;     }     for (long long i = 0; i < adj[v].size(); i++) {       long long u = adj[v][i];       if (u != l) dfs_down(u, v, edg[v][i]);       if (u == l) {         inc[v].push_back(0);         continue;       }       zt[v] += zt[u];       sum[v] += sum[u];       sum[v] %= mod;       sum[v] += edg[v][i] * zt[u];       sum[v] %= mod;       long long res = mrg(dp[u], edg[v][i], sum[u], zt[u]);       inc[v].push_back(res);       dp[v] += res;       dp[v] %= mod;     }     dp2[v] = dp[v];   }   void dfs_up(long long v, long long l, long long c, long long cc) {     if (v == 1) sum2[v] = sum[v];     if (v != 1) {       sum2[v] += (sum2[l] - ((cc * zt[v] + sum[v]) % mod) + mod) % mod;       sum2[v] %= mod;       long long res = dp[l] - c;       res += mod;       res %= mod;       dp[v] += mrg(res, cc, sum2[v], n - zt[v]);       dp[v] %= mod;       sum2[v] += sum[v];       sum2[v] %= mod;       sum2[v] += cc * (n - zt[v]);       sum2[v] %= mod;     }     for (long long i = 0; i < adj[v].size(); i++) {       long long u = adj[v][i];       if (u != l) dfs_up(u, v, inc[v][i], edg[v][i]);     }   }   long long lca(long long v, long long u) {     if (h[v] < h[u]) swap(v, u);     for (long long i = 20; i >= 0; i--) {       if (h[v] - (1 << i) >= h[u]) len += val[v][i], v = par[v][i];     }     len %= mod;     if (v == u) return v;     for (long long i = 20; i >= 0; i--) {       if (par[v][i] != par[u][i])         len += val[v][i], len += val[u][i], v = par[v][i], u = par[u][i];     }     len += val[v][0];     len += val[u][0];     len %= mod;     v = par[v][0];     return v;   }   int32_t main() {     cin >> n;     for (long long i = 1; i <= n - 1; i++) {       long long a, b, c;       cin >> a >> b >> c;       adj[a].push_back(b);       adj[b].push_back(a);       edg[a].push_back(c);       edg[b].push_back(c);     }     dfs_down(1, 0, 0);     dfs_up(1, 0, 0, 0);     long long q;     cin >> q;     while (q--) {       long long v, u;       cin >> u >> v;       len = 0;       long long lc = lca(u, v);       len %= mod;       long long all = 0;       if (lc != v) {         all = -dp[u];         all += mod;         all %= mod;         long long res = mrg(dp2[v], len, sum[v], zt[v]);         all += res * 2;         all %= mod;       } else {         all = dp[u];         long long res = sum2[v] - sum[v];         long long bad = dp[v] - dp2[v];         bad += mod;         bad %= mod;         res += mod;         res %= mod;         long long hlp = mrg(bad, len, res, n - zt[v]);         all -= 2 * hlp;         all += 3 * mod;         all %= mod;       }       cout << all <<   n ;     }   }   