#include <bits/stdc++.h>
using namespace std;
inline int Int() {
  int x;
  scanf("%d", &x);
  return x;
}
inline long Long() {
  long x;
  scanf("%ld", &x);
  return x;
}
inline long long LLong() {
  long long x;
  scanf("%lld", &x);
  return x;
}
inline float Float() {
  float x;
  scanf("%f", &x);
  return x;
}
inline float Double() {
  double x;
  scanf("%lf", &x);
  return x;
}
inline pair<int, int> Pair() {
  pair<int, int> p;
  scanf("d %d", &p.first, &p.second);
  return p;
}
void S(char *x) { scanf("%s", x); }
void pI(int x) { printf("%d", x); }
void pL(long x) { printf("%ld", x); }
void pLL(long long x) { printf("%lld", x); }
void pUL(unsigned long long x) { printf("%llu", x); }
void pF(float x) { printf("%f", x); }
void pD(double x) { printf("%f", x); }
void pS(char x[]) { printf("%s", x); }
int dx8[] = {0, 0, 1, 1, 1, -1, -1, -1};
int dy8[] = {1, -1, 1, -1, 0, 0, -1, 1};
const double pi = acos(-1.0);
const double eps = 1e-6;
const int mod = (int)1e9 + 7;
const int maxn = (int)1e5 + 5;
const int logn = 20;
vector<int> g[maxn], cost[maxn];
int ans;
int a[maxn];
int sub[maxn];
long long mx_path_cost[maxn];
void dfs(int u, int p) {
  sub[u] = 1;
  for (int i = 0; i < (g[u].size()); i++) {
    int v = g[u][i];
    if (v == p) continue;
    mx_path_cost[v] = max(mx_path_cost[u] + cost[u][i], 0LL);
    dfs(v, u);
    sub[u] += sub[v];
  }
  if (mx_path_cost[u] > a[u]) {
    ans += sub[u];
    sub[u] = 0;
  }
}
int main() {
  int n = Int();
  for (int i = 1; i <= (n); i++) a[i] = Int();
  for (int i = 1; i <= (n - 1); i++) {
    int u = Int(), v = i + 1, w = Int();
    g[u].push_back(v);
    g[v].push_back(u);
    cost[u].push_back(w);
    cost[v].push_back(w);
  }
  dfs(1, 0);
  pI(ans);
  printf("\n");
  return 0;
}
