#include<bits/stdc++.h>
using namespace std;

long long int l[200005] = {0};

int main(){
    long long int n;
    cin >> n;
    for(int i=0;i<n;++i)cin >> l[i];
    long long int k;
    cin >> k;

    long double ok = 0, ng = 1e9 + 1;
    while(abs(ng-ok) > 1e-10){
        long double mid = (ok + ng) / 2.0;
        long long int cnt = 0;
        for(int i=0;i<n;++i)
            cnt += floor(l[i] / mid);
        if(cnt >= k)ok = mid;
        else ng = mid;
    }

    printf("%.10Lf\n",ok);

    return 0;
}