#include <bits/stdc++.h>
using namespace std;
using LL = long long;
const int N = 1e5 + 10;

LL most[N], fa[N], val[N], ck[N];
void solve()
{
    int n;
    cin >> n;
    for(int i = 1; i <= n; i++) {
        cin >> fa[i] >> most[i];
        val[fa[i]] = 0;
        val[i] = most[i];
        ck[fa[i]] = 1;
    }

    LL cnt = 0, need = 0, have = 0;
    for(int i = n; i >= 1; i--) {
        if(val[i] > most[i]) {
            cnt++;
            need = val[i], have = most[i];
        }
        val[fa[i]] += val[i];
    }
    if(cnt > 1 || val[0] > 2200) {
        cout << "NO";
        return;
    }

    else if(cnt == 0) {
        cout << "YES";
        return;
    }

    for(int i = 0; i <= n; i++) {
        if(!ck[i]) continue;
        if(val[i] <= have && most[i] >= need) {
            cout << "YES";
            return;
        }
    }
    cout << "NO";
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t;
    t = 1;
    // cin >> t;
    while(t--) solve();
    return 0;
}