#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int N; cin >> N;
    using ld = long double;
    vector<ld> L(N);
    rep(i,N) cin >> L[i];
    ll K; cin >> K;

    auto f = [&](ld x) {
        ll cnt = 0;
        rep(i,N) cnt += floorl(L[i] / x);
        return K <= cnt;
    };

    ld ok = 0.0, ng = 1e18;
    int step = 100;

    rep(_,step) {
        ld mid = (ok + ng) * 0.5;
        (f(mid) ? ok : ng) = mid;
    }

    cout << fixed << setprecision(20) << ok << endl;
}