#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f;
const long long infl = 0x3f3f3f3f3f3f3f3fLL;
const int MAXN = 1000006;
int n, m, u;
long long h;
long long L[MAXN];
vector<long long> dep[MAXN], pre[MAXN];
void dfs(int rt) {
  if (rt > n) return;
  dep[rt].clear();
  pre[rt].clear();
  dep[rt].push_back(0);
  int lch = rt << 1, rch = rt << 1 | 1;
  dfs(lch);
  dfs(rch);
  int i = 0, j = 0;
  if (lch <= n && rch <= n) {
    while (i < dep[lch].size() && j < dep[rch].size()) {
      long long a = dep[lch][i] + L[lch];
      long long b = dep[rch][j] + L[rch];
      if (a <= b)
        dep[rt].push_back(a), ++i;
      else
        dep[rt].push_back(b), ++j;
    }
  }
  while (lch <= n && i < dep[lch].size())
    dep[rt].push_back(dep[lch][i++] + L[lch]);
  while (rch <= n && j < dep[rch].size())
    dep[rt].push_back(dep[rch][j++] + L[rch]);
  pre[rt].resize(dep[rt].size());
  pre[rt][0] = dep[rt][0];
  for (int i = 1; i < dep[rt].size(); ++i) {
    pre[rt][i] = pre[rt][i - 1] + dep[rt][i];
  }
}
int main() {
  scanf("%d %d", &n, &m);
  for (int i = 2; i <= n; ++i) scanf("%lld", &L[i]);
  dfs(1);
  for (int i = 1; i <= m; ++i) {
    scanf("%d %lld", &u, &h);
    int pos = lower_bound(dep[u].begin(), dep[u].end(), h) - dep[u].begin();
    long long ans = 0;
    if (pos != 0) ans += pos * h - pre[u][pos - 1];
    while (u > 1 && h - L[u] > 0) {
      h -= L[u];
      ans += h;
      int v = u ^ 1;
      if (h - L[v] > 0) {
        long long hx = h - L[v];
        pos = lower_bound(dep[v].begin(), dep[v].end(), hx) - dep[v].begin();
        if (pos != 0) ans += pos * hx - pre[v][pos - 1];
      }
      u >>= 1;
    }
    printf("%lld\n", ans);
  }
  return 0;
}
