#include <iostream>
#include <algorithm>
#include <vector>
#include <iomanip>
using namespace std;

int main(){
    int N;
    cin >> N;
    long sticks[N];
    for(int i = 0; i < N; i++){
        cin >> sticks[i];
    }
    long K;
    cin >> K;
    double left = 0, right = 1e18;
    for(int i = 0; i < 100; i++){
        double middle = (left + right) / 2;
        long get_stick = 0;
        for(int j = 0; j < N; j++){
            get_stick += sticks[j] / middle;
        }
        if(get_stick >= K){
            left = middle;
        }else{
            right = middle;
        }
    }
    cout << fixed << setprecision(15) << left << endl;
}