/*** WORK : 省赛\2024大连省赛\c.cpp ***/
/*** TIME : 2024/11/27 16:37 ***/
#include<bits/stdc++.h>
using namespace std;
#define all(v) v.begin(),v.end()
#define pb push_back
#define se second
#define fi first
#define int long long
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
const int MOD = (int) 1e9 + 7;
const int INF = LLONG_MAX;



void solve() {
    int n;
    cin >> n;
    vvi e(n+1,vi());
    vi w(n+1);
    vi root;
    for(int i=1;i<=n;i++){
        int fa;
        cin >> fa >> w[i];
        e[fa].push_back(i);
        if(fa == 0)root.pb(i);
    }
    // for(int x:e[1]){cout << x <<"  ";cout << endl;}
    vi lead,dp(n+1,0);
    multiset<int> use;
    int sum = 0;
    for(int i=1;i<=n;i++){
        if(e[i].size()==0){
            lead.pb(i);
            sum += w[i];
            dp[i] = w[i];
        }else{
            use.insert(w[i]);
        }
    }
    if(sum > 2200){
        cout << "NO" << endl;
        exit(0);
    }
    use.insert(INF);
    auto dfs = [&](auto&& dfs,int u,int fa)->void{
        if(e[u].size()==0)return;
        for(int v:e[u]){
            if(v==fa)continue;
            dfs(dfs,v,u);
            dp[u] += dp[v];
        }
        auto f = *use.lower_bound(dp[u]);
        // cout << u << " " << dp[u] << " " << f << endl;
        if(f == INF){
            cout << "NO" << endl;
            exit(0);
        }
        use.erase(f);
    };
    if(root.size() > 1){
        cout << "NO" << endl;
        return;
    }
    // for(int rr : root){
        dfs(dfs,root[0],0);
    // }
    cout << "YES" << endl;    
}

int32_t main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    cout << fixed << setprecision(12);
    int T = 1;
    T=1;
    while (T--)solve();
}