func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 2e6 + 7;   const long long MOD = 1e9 + 7;   template <class T>   bool umin(T& a, T b) {     if (a > b) {       a = b;       return 1;     }     return 0;   }   template <class T>   bool umax(T& a, T b) {     if (a < b) {       a = b;       return 1;     }     return 0;   }   template <class T>   bool umod(T& a, T b) {     a += b;     while (a < 0) a += MOD;     a %= MOD;     return 1;   }   int las, n, cur, cost[N], m, cst;   vector<int> v[N];   vector<long long> par[N];   long long ans;   void merge(int x) {     v[x].push_back(0);     int l = x * 2, r = x * 2 + 1;     int a = 0, b = 0;     while (a < int(v[l].size()) && b < int(v[r].size())) {       if (v[l][a] + cost[l] <= v[r][b] + cost[r])         v[x].push_back(v[l][a] + cost[l]), a++;       else         v[x].push_back(v[r][b] + cost[r]), b++;     }     while (a < int(v[l].size())) v[x].push_back(v[l][a] + cost[l]), a++;     while (b < int(v[r].size())) v[x].push_back(v[r][b] + cost[r]), b++;     par[x].push_back(0LL);     for (int i = 1; i < int(v[x].size()); i++)       par[x].push_back(par[x][i - 1] + v[x][i]);   }   void dfs(int x) {     if (x > n) return;     dfs(x * 2);     dfs(x * 2 + 1);     merge(x);   }   long long get(int x, int y) {     if (x > n || y <= 0) return 0;     int ind = upper_bound(v[x].begin(), v[x].end(), y) - v[x].begin();     return 0LL + (1LL * ind * y) - par[x][ind - 1];   }   int main() {     scanf( %d%d , &n, &m);     for (int i = 2; i <= n; i++) scanf( %d , &cost[i]);     dfs(1);     while (m--) {       int aa, bb;       scanf( %d%d , &aa, &bb);       las = -1, cur = aa, ans = 0, cst = bb;       while (las != 1 && cst > 0) {         if (las != cur * 2) ans += get(cur * 2, cst - cost[cur * 2]);         if (las != cur * 2 + 1) ans += get(cur * 2 + 1, cst - cost[cur * 2 + 1]);         ans += cst;         cst -= cost[cur];         las = cur;         cur /= 2;       }       printf( %lld n , ans);     }     return 0;   }   