#include <bits/stdc++.h>
using namespace std;
namespace std {
template <class S, class T>
struct hash<pair<S, T>> {
  size_t operator()(const pair<S, T> &p) const {
    return ((size_t)1e9 + 7) * hash<S>()(p.first) + hash<T>()(p.second);
  }
};
template <class T>
struct hash<vector<T>> {
  size_t operator()(const vector<T> &v) const {
    size_t h = 0;
    for (auto i : v) h = h * ((size_t)1e9 + 7) + hash<T>()(i) + 1;
    return h;
  }
};
}  // namespace std
template <class T>
ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "[ ";
  for (int i = 0; i < (int)v.size(); i++)
    os << v[i] << (i == v.size() - 1 ? " ]" : ", ");
  return os;
}
template <class T>
ostream &operator<<(ostream &os, const set<T> &v) {
  os << "{ ";
  for (const auto &i : v) os << i << ", ";
  return os << "}";
}
template <class T, class U>
ostream &operator<<(ostream &os, const map<T, U> &v) {
  os << "{";
  for (const auto &i : v) os << " " << i.first << ": " << i.second << ",";
  return os << "}";
}
template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  return os << "(" << p.first << ", " << p.second << ")";
}
void dbgprint(const string &fmt) { cerr << endl; }
template <class H, class... T>
void dbgprint(const string &fmt, const H &h, const T &...r) {
  cerr << fmt.substr(0, fmt.find(",")) << "= " << h << " ";
  dbgprint(fmt.substr(fmt.find(",") + 1), r...);
}
const int inf = (int)1e9;
const double INF = 1e12, EPS = 1e-9;
int n, a[100010], ans;
vector<pair<int, int>> e[100010];
bool sad[100010];
map<long long, int> cnt;
void rec(int c, int p, long long dist) {
  if (cnt.size() && a[c] < dist - cnt.begin()->first) sad[c] = 1;
  cnt[dist]++;
  for (pair<int, int> i : e[c])
    if (i.first != p) {
      rec(i.first, c, dist + i.second);
    }
  if (--cnt[dist] == 0) cnt.erase(dist);
}
void rec(int c, int p) {
  ans--;
  for (pair<int, int> i : e[c])
    if (i.first != p && !sad[i.first]) {
      rec(i.first, c);
    }
}
int main() {
  cin.tie(0);
  cin.sync_with_stdio(0);
  cin >> n;
  for (int i = 0; i < (int)n; i++) cin >> a[i];
  for (int i = 0; i < (int)n - 1; i++) {
    int p, w;
    cin >> p >> w;
    p--;
    e[i + 1].push_back(make_pair(p, w));
    e[p].push_back(make_pair(i + 1, w));
  }
  ans = n;
  rec(0, 0, 0);
  rec(0, 0);
  cout << ans << endl;
  return 0;
}
