[ABC309E] Family and Insurance

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 3e5 + 10;
vector<int> Edge[N];
int n, m, x, y, ans, now[N];
bool ok[N];
void dfs(int x) {
    if(now[x]) ok[x] = 1;
    for (int i : Edge[x])
        now[i] = max(now[i], now[x] - 1);
    for (int i : Edge[x])
        dfs(i);
}
signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
    for (int i = 2; i <= n; i++)
        cin >> x, Edge[x].push_back(i);
    for (int i = 1; i <= m; i++)
        cin >> x >> y, now[x] = max(now[x], y + 1);
    dfs(1);
    for (int i = 1; i <= n; i++) ans += ok[i];
    cout << ans;
    return 0;
}