#include <bits/stdc++.h>
using namespace std;
int main(){
float n,a[250],c,v,x=0;
cin>>n>>c;
for(int i=1;i<=n;i++){
	cin>>a[i];
}
for(int i=1;i<=n;i++){
if(a[i]==c){
	v++;
}

}
x=v/n;
printf("%.2f",x);
    return 0;
}
/**************************************************************
	Problem: 1354
	User: wangyousi
	Language: C++
	Result: Wrong Answer
****************************************************************/