#include <bits/stdc++.h>
using namespace std;
long long A[100005], Nr[100005], Viz[100005];
vector<pair<long long, long long> > V[100005];
long long n;
long long ans;
long long DFSNR(long long x) {
  long long nrc = 1;
  Viz[x] = 1;
  for (auto i : V[x])
    if (!Viz[i.first]) {
      nrc += DFSNR(i.first);
    }
  Nr[x] = nrc;
  return nrc;
}
void DFS(long long x, long long dist) {
  if (A[x] < dist) {
    ans += Nr[x];
    return;
  }
  Viz[x] = 1;
  for (auto i : V[x])
    if (!Viz[i.first]) {
      DFS(i.first, max(dist + i.second, i.second));
    }
}
int main() {
  cin >> n;
  for (long long i = 1; i <= n; i++) cin >> A[i];
  for (long long i = 1; i < n; i++) {
    long long x, y;
    cin >> x >> y;
    V[x].push_back({i + 1, y});
    V[i + 1].push_back({x, y});
  }
  DFSNR(1);
  memset(Viz, 0, sizeof(Viz));
  DFS(1, 0);
  cout << ans;
  return 0;
}
