#include <bits/stdc++.h>

#define show(x) cout << #x << " = " << x << endl

using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    os << "sz=" << v.size() << "\n[";
    for (const auto& p : v) {
        os << p << ",";
    }
    os << "]\n";
    return os;
}

template <typename S, typename T>
ostream& operator<<(ostream& os, const pair<S, T>& p)
{
    os << "(" << p.first << "," << p.second
       << ")";
    return os;
}


constexpr ll MOD = 1e9 + 7;

template <typename T>
constexpr T INF = numeric_limits<T>::max() / 100;

int main()
{
    ll N;
    cin >> N;
    vector<ll> L(N);
    for (ll i = 0; i < N; i++) {
        cin >> L[i];
    }
    ll K;
    cin >> K;

    constexpr long double eps = 1e-9;
    long double inf = 0;
    long double sup = 1e9;
    while (abs(inf - sup) > eps) {
        const long double mid = (inf + sup) / 2;
        ll num = 0;
        for (ll i = 0; i < N; i++) {
            num += static_cast<ll>(floorl(static_cast<long double>(L[i]) / mid));
        }
        if (num < K) {
            sup = mid;
        } else {
            inf = mid;
        }
    }
    cout << fixed << setprecision(10) << inf << endl;

    return 0;
}