#include<bits/stdc++.h>
using namespace std;
const int N=100005;
int n,m,a[N];
int main()
{
    scanf("%d%d",&n,&m);
    int sum=0,mx=0;
    double sqrsum=0;
    for (int i=1;i<=n;++i)
    {
        scanf("%d",&a[i]);
        mx=max(mx,a[i]);
        sum+=a[i];
        sqrsum+=sqrt(a[i]);
    }
    double t1=(double)sum/mx,t2=0;
    for (int i=1;i<=n;++i)
        t2+=(double)sqrt(a[i])*sqrsum;
    t2=t2/sum;
    // printf("%lf %lf\n",t1,t2);
    printf("%.9lf\n",(t1*m+t2*(100-m))/100.0);
    return 0;
}