#include <iostream>
#include <vector>
#include <algorithm>

#define int long long

using namespace std;

vector<int> son[100001];
int w[100001],depth[100001],sum[100001],curr=0;
vector<int> save;

void dfs(int u)
{
	int maxi=0;
	
	for(auto v:son[u])
	{
		dfs(v);
		
		maxi=max(maxi,depth[v]);
	}
	
	depth[u]=maxi+1;
	
	return;
}

void dfs2(int u)
{
	if((int)son[u].size()==0)
	{
		sum[u]=w[++curr];
		
		return;
	}
	
	for(auto v:son[u]){
		dfs2(v);
		
		sum[u]+=sum[v];
	}
	
	save.push_back(sum[u]);
	
	return;
}

bool cmp(int x,int y)
{
	return depth[x]>depth[y];
}

signed main()
{
	ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
	
	int n;
	
	cin>>n;
	for(int i=1;i<=n;i++){
		int fa;
		cin>>fa>>w[i];
		
		son[fa].push_back(i);
	}
	
	sort(w+1,w+n+1);
	
	dfs(0);
	
	for(int i=0;i<=n;i++){
		sort(son[i].begin(),son[i].end(),cmp);
	}
	
	dfs2(0);
	
	sort(save.begin(),save.end());
	for(int i=curr+1,j=0;i<=n;i++,j++)
	{
		if(save[j]>w[i])
		{
			cout<<"NO\n";
			return 0;
		}
	}
	
	if(sum[0]<=2200) cout<<"YES\n";
	else cout<<"NO\n";
	
	return 0;
}