#include<stdio.h>

int main(){
	int n,i;
	long sum=0,x,a;
	scanf("%d %ld",&n,&a);
	for(i=n;i>0;i--){
		scanf("%ld",&x);
		sum+=x;
	}
	if(((sum/(long)n)==a) && (sum%(long)n==0)) printf("YES\n");
	else printf("NO\n");
	return 0;
}