#include<cstdio>

#include<algorithm>

#include<cstring>

#include<cmath>

#define N 10010

using namespace std;

double L[N],l,r,mid;

long long n,k;

//yjjsb

bool check(double lim)

{

    int ret=0;

    for (int i=1;i<=n;i++)

	ret+=int(floor(L[i]/lim));

    return ret>=k;

}

int main()

{

    scanf("%lld%lld",&n,&k);

    for (int i=1;i<=n;i++)

	scanf("%lf",&L[i]),r+=2*L[i];

    for (int i=1;i<=100;i++)

    {

	mid=(l+r)/2;

	if (check(mid)) l=mid;

	else r=mid;

    }

    printf("%.2f",floor(r*100)/100);

    return 0;

}