#include<stdio.h>

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