#include <bits/stdc++.h>
using namespace std;
struct vertex {
  long long inside, edge;
  int size = 1;
  vector<int> child;
};
int ans = 0;
multiset<long long> st;
vertex g[100009];
void dfs(int v, bool flag, long long deep) {
  if (flag) {
    for (int i = 0; i < g[v].child.size(); i++) {
      dfs(g[v].child[i], 1, 0);
      g[v].size += g[g[v].child[i]].size;
    }
    return;
  }
  if (deep - g[v].inside > *st.begin()) flag = 1;
  st.insert(deep);
  for (int i = 0; i < g[v].child.size(); i++) {
    dfs(g[v].child[i], flag, deep + g[g[v].child[i]].edge);
    g[v].size += g[g[v].child[i]].size;
  }
  if (flag) ans += g[v].size;
  flag = 0;
  st.erase(deep);
}
int main() {
  ios_base::sync_with_stdio(0);
  int n;
  st.insert(100000000000000000);
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> g[i].inside;
  for (int i = 2, c; i <= n; i++) {
    cin >> c >> g[i].edge;
    g[c].child.push_back(i);
  }
  dfs(1, 0, 0);
  cout << ans;
  return 0;
}
