#pragma GCC optimize(3)
#include <bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define N 100005
#define MOD 998244353
using namespace std;
multiset<int> w;
int n,a[N];
int siz[N];
vector<int> e[N];
void dfs(int u)
{
    if(e[u].size()==0) {siz[u]=a[u];}
    else {siz[u]=0; if(u!=0) w.insert(a[u]);}
    for(auto &&v:e[u])
    {
        dfs(v);
        siz[u] += siz[v];
    }
}
void solve()
{
    cin>>n;
    for(int i=1;i<=n;++i)
    {
        int f;
        cin>>f>>a[i];
        e[f].push_back(i);
    }
    dfs(0);
    if(siz[0]>2200) {cout<<"NO\n"; return;}
    for(int i=1;i<=n;++i)
    {
        if(e[i].size() != 0)
        {
            auto it = w.lower_bound(siz[i]);
            if(it == w.end()) {cout<<"NO\n"; return;}
            else w.erase(it);
        }
    }
    cout<<"YES\n";
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int T=1;
    // cin>>T;
    while(T--)
    {
        solve();
    }
    return 0;
}