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

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N; cin >> N;
    vector<double> L(N);
    for(auto &l : L) cin >> l;

    long long K; cin >> K;
    double low = 0,high = 1001001001;
    for(int t=0; t<100; t++){
        double mid = (high+low)/2;
        long long cut = 0;
        for(auto l : L) cut += floor(l/mid);
        if(cut >= K) low = mid;
        else high = mid;
    }
    cout << fixed << setprecision(20) << low << endl;
}