#include <iostream>
using namespace std;

int main()
{
	long long n,a,b;
	b=0;
	cin>>n>>a;
	for(int i=0;i<=n;i++){
		int x;cin>>x;
		b+=x;
	}
	if((a==b/n))
		cout<<"YES"<<endl;
	else;
		cout<<"NO"<<endl;

	

}