#include<bits/stdc++.h>
#define ll  long long
#define ull unsigned long long
#define ld long double
#define pii pair<ll,ll>
using namespace std;
//#pragma GCC optimize(3)
const ll inf =(1ll<<50);
#define N 1000005
#define M 998244353
#define M1 1000000007
#define M2 1000000009
vector<ll> v[N];
ll sum[N],fa[N],a[N],flag;
vector<ll> st;
void dfs(ll p)
{
    if(flag) return;
    for(int i=0;i<v[p].size();i++)
    {
        dfs(v[p][i]);
        sum[p]+=sum[v[p][i]];
    }
    if(!v[p].size())
    {
        sum[p]=a[p];
    }
    else if(p!=0)
    {
        auto it= lower_bound(st.begin(),st.end(),sum[p]);
        if(it==st.end())
        {
            flag=1;
            return;
        }
     //   cerr<<sum[p]<<*it<<endl;
        st.erase(it);
    }
}
int main()
{
   ios::sync_with_stdio(0);
   cin.tie(0);
   cout.tie(0);
    ll n;
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        cin>>fa[i]>>a[i];
        v[fa[i]].push_back(i);
    }
    for(int i=1;i<=n;i++)
    {
        if(v[i].size())
        {
           st.push_back(a[i]);
        }
    }

    sort(st.begin(),st.end());
    dfs(0);
    if(sum[0]>2200) flag=1;
    if(flag) cout<<"NO"<<endl;
    else cout<<"YES"<<endl;
    return 0;
}
//5
//0 500
//1 700
//1 400
//2 100
//2 300