#include <stdio.h>

int main(void)
{
    int n,i;
    long int a,num,sum = 0;

    scanf("%d",&n);
    scanf("%ld",&a);
    for(i = 0;i < n;i++){
        scanf("%ld",&num);
        sum += num;
    }
    if (sum == n*a){
        printf("YES\n");
    } else {
        printf("NO\n");
    }
    return 0;
}