#include<bits/stdc++.h>
using namespace std;
using ll=long long;
using i64=long long;
using u64=unsigned long long;
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin>>n;
    vector<vector<int>> g(n+1);
    vector<int> a(n+1);
    for(int i=1;i<=n;i++){
        int x;
        cin>>x;
        g[x].push_back(i);
        cin>>a[i];        
    }
    a[0]=2200;
    vector<ll> siz(n+1);
    vector<ll> b;
    vector<ll> c;
    auto dfs=[&](auto dfs,int x)->void{
        if(g[x].size()==0){
            siz[x]=a[x];
            return;
        }
        for(auto y:g[x]){
            dfs(dfs,y);
            siz[x]+=siz[y];
        }
        c.push_back(siz[x]);
        b.push_back(min(2200,a[x]));
        
    };
    dfs(dfs,0);
    sort(b.begin(),b.end());
    sort(c.begin(),c.end());
    
    for(int i=0;i<b.size();i++){
        if(c[i]>b[i]){
            //cout<<c[i]<<" "<<b[i]<<"\n";
            cout<<"NO"<<'\n';
            return 0;
        }
    }
    cout<<"YES"<<"\n";
    return 0;
}