#include <cstdio>
#include <cstring>
#include <algorithm>
#define ll long long

using namespace std;

int read()
{
	int a = 0,x = 1;char ch = getchar();
	while(ch > '9' || ch < '0') {if(ch == '-') x = -1;ch = getchar();}
	while(ch >='0' && ch <= '9') {a = a*10 + ch-'0';ch = getchar();}
	return a*x;
}
const int N = 5e6+7;
int head[N],go[N],nxt[N],cnt;
void add(int u,int v)
{
	go[++cnt] = v;
	nxt[cnt] = head[u];
	head[u] = cnt;
}

int n,du[N];
ll f[N],arr[N];
void dfs(int u,int fa)
{
	if(du[u] == 0) f[u] = arr[u];
	for(int e = head[u];e;e = nxt[e]) {
		int v = go[e];if(v == fa) continue;
		dfs(v,u);f[u] += f[v];
	}
}
int main()
{
	// freopen("in.in","r",stdin);freopen("out.out","w",stdout);
	n = read();
	for(int i = 1;i <= n;i ++) {
		int fa = read();arr[i] = read();
		add(fa,i);du[fa] ++;
	}
	dfs(0,0);if(f[0] > 2200) {puts("NO");return 0;}
	sort(arr+1,arr+1+n);sort(f+1,f+1+n);
	for(int i = 1;i <= n;i ++) {
		if(f[i] > arr[i]) {puts("NO");return 0;}
	}
	printf("YES\n");
}