#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

int main()
{
    int n;
    cin >> n;
    vector<int> len(n);
    for(int i=0; i<n; ++i)
        cin >> len[i];

    long long k;
    cin >> k;

    double a = 0;
    double b = 1000000000;
    for(int i=0; i<100; ++i){
        double x = (a + b) / 2;
        long long cnt = 0;
        for(int j=0; j<n; ++j)
            cnt += (long long)(len[j] / x);

        if(cnt < k)
            b = x;
        else
            a = x;
    }
    printf("%.10f\n", a);

    return 0;
}