#include<bits/stdc++.h>
#define ll long long
using namespace std;
const int N=1e6+10;
ll n,c,a[N],sum[N];
double f[N];
int main(){
	freopen("card.in","r",stdin);
	freopen("card.out","w",stdout);
	cin>>n>>c;
	for(int i=1;i<=n;i++)scanf("%lld",&a[i]);
	sort(a+1,a+n+1,[](int x,int y){return x>y;});
	for(int i=1;i<=n;i++)sum[i]=sum[i-1]+a[i];
	for(int i=1,j=1;i<=n;i++){
		f[i]=sum[j]+f[i-1]*(i-j);
		while(j<i&&sum[j+1]+f[i-1]*(i-j-1)>f[i])j++,f[i]=sum[j]+f[i-1]*(i-j);
		f[i]=f[i]/i-c;
	}
	printf("%.12lf",f[n]);
}