#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;
}
