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

#define REP(i, n) for (int i = 0; i < (n); ++i)
#define P(x) cout << (x) << "\n"
#define D(x) cerr << (x) << "\n"
#define fcout cout << fixed << setprecision(18)

using i64 = long long int; // 10^18
static const double eps = (1e-10);

vector<double> l;
i64 k;
bool isOK(double s)
{
    double sum = 0;
    for (auto ll : l)
    {
        sum += (i64)floor(ll / s);
    }
    return sum >= k;
}
double binary_search()
{
    double ng = 0;
    double ok = 10000000000;
    int i=0;
    while (i<100)
    {
        double mid = ng + (double (ok - ng)) / 2;
        if (!isOK(mid))
        {
            ok = mid;
        }
        else
        {
            ng = mid;
        }
        i++;
    }
    return ok;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n;
    cin >> n;
    REP(i, n)
    {
        double ll;
        cin >> ll;
        l.push_back(ll);
    }
    cin >> k;
    fcout<< binary_search() <<endl;
    return 0;
}