#include <bits/stdc++.h>

using i64 = long long;
using u64 = unsigned long long;

void solve() {
    int n;
    std::cin >> n;

    n += 1;

    std::vector<int> r(n);
    r[0] = 2200;
    std::vector<std::vector<int>> adj(n);
    for(int i = 1; i < n; i ++ ) {
        int f, v;
        std::cin >> f >> v;
        adj[f].push_back(i);
        r[i] = v;
    }
    
    std::vector<int> w(n);
    int ned = -1, cnt = 0, ok = false;
    auto dfs = [&](auto &self, int x, int p) -> void {
        if(not adj[x].size()) {
            w[x] = r[x];
            return;
        }
        for(auto y : adj[x]) {
            if(y == p) continue;
            self(self, y, x);
            w[x] += w[y];
        }

        if(r[x] < w[x]) {
            ned = x;
            cnt += 1;
        }
    };

    dfs(dfs, 0, -1);
    for(int i = 1; i < n; i ++ ) {
        if(r[i] >= w[i]) {
            if(r[i] >= w[ned] and r[ned] >= w[i]) {
                ok = true;
            }
        }
    }
    if(cnt == 1 and ok or cnt == 0) {
        std::cout << "YES" << '\n';
    } else {
        std::cout << "NO" << '\n';
    }

}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int T = 1;
    // std::cin >> T;

    while(T -- ) {
        solve();
    }

    return 0;
}