// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC target ("avx,avx2,fma")
#include <bits/stdc++.h>

#define rep(i, a, b) for(int i = (a); i <= (b); i ++)
using std::cin, std::cout, std::cerr;
using ll = long long;

int main() {
    std::ios::sync_with_stdio(false);
    int n; cin >> n;
    std::vector<double> a(n);
    rep(i, 0, n - 1) cin >> a[i];
    double l = 0, r = 1e9;
    int k; cin >> k;
    while(r - l > 1e-12) {
        double m = (l + r) / 2;
        double cnt = 0;
        for(double x : a)
            cnt += int(x / m);
        if(cnt >= k)
            l = m;
        else
            r = m;
    }
    cout << std::fixed << std::setprecision(12);
    cout << l << '\n';
}