//No.480 合計

#include <bits/stdc++.h>
using namespace std;

int main()
{
int i;
int n;
int a;
int x;
int iSum;

	cin >> n;
	cin >> a;

	iSum = 0;
	for( i = 0; i < n; i++ )
	{
		cin >> x;
		iSum += x;
	}

	if( iSum % n == 0 && iSum / n == a )
		cout << "YES" << endl;
	else
		cout << "NO" << endl;

	return 0;
}