#include<bits/stdc++.h>
using namespace std;
using Int = long long;
//INSERT ABOVE HERE
signed main(){
  Int n,a;
  cin>>n>>a;
  vector<Int> x(n);
  for(Int i=0;i<n;i++) cin>>x[i];
  Int s=accumulate(x.begin(),x.end(),(Int)0);
  cout<<(s==a*n?"YES":"NO")<<endl;
  return 0;
}