#include <stdio.h>

int main()
{
	long long n, a = 0;
	scanf("%lld%lld", &n, &a);

	int sum = 0;

	for (int i = 0; i < n; i++)
	{
		int x;
		scanf("%d", &x);
		sum += x;
	}

	long long f = n * a;

	if (f == (long long)sum)
	{
		printf("YES");
	}
	else
	{
		printf("NO");
	}

	return 0;
}