#include<bits/stdc++.h>
using namespace std;
#define il inline
#define fi first
#define se second
#define mk make_pair
#define eb emplace_back
#define rep(i,l,r) for(int i=(l); i<=(r); ++i)
#define rep_(i,l,r) for(int i=(l); i>=(r); --i)
typedef long long lr;
typedef double db;
typedef pair<int,int> pii;
typedef vector<int> vi;
constexpr int mod1=998244353,mod2=1e9+7;
constexpr db pi=3.141592653589793,eps=1e-9;
constexpr int inf32=0x3f3f3f3f,Inf32=0xc0c0c0c0;
constexpr lr inf64=0x3f3f3f3f3f3f3f3f,Inf64=0xc0c0c0c0c0c0c0c0;
template<typename T>il T Max(T x,T y) { return (x>y)? x:y; }
template<typename T>il T Min(T x,T y) { return (x<y)? x:y; }
template<typename T>il T gcd(T x,T y) { return (!y)? x:gcd(y,x%y); }
template<typename T>il T Abs(T x) { return (x>0)? x:(-x); }
template<typename T>il T Rnd(T l,T r,mt19937_64 &eng)
{
	uniform_int_distribution<T> uid(l,r);
	return uid(eng);
}
mt19937_64 eng(chrono::high_resolution_clock::now().time_since_epoch().count());
constexpr int N=100100;
int n,x,b[N],d[N];
lr c[N],e[N];
vi v[N];
il void dfs(int u)
{
	if(v[u].empty())
	{
		c[u]=b[u];
		return;
	}
	for(int to:v[u])
		dfs(to),c[u]+=c[to];
}
il void Solve()
{
	cin>>n;
	rep(i,1,n)
		cin>>x>>b[i],v[x].eb(i);
	dfs(0);
	if(c[0]>2200)
	{
		cout<<"NO\n";
		return;
	}
	int m=0;
	rep(i,1,n)
		if(!v[i].empty())
			d[++m]=b[i],e[m]=c[i];
	sort(d+1,d+1+m);
	sort(e+1,e+1+m);
	rep(i,1,m)
		if(d[i]<e[i])
		{
			cout<<"NO\n";
			return;
		}
	cout<<"YES\n";
}
int main()
{
#ifdef LOCAL
	string fpre="test",isuf="in",osuf="out";
	assert(freopen((fpre+"."+isuf).c_str(),"r",stdin));
	assert(freopen((fpre+"."+osuf).c_str(),"w",stdout));
#endif
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	int T=1;
	while(T--)
		Solve();
	return 0;
}