#include "bits/stdc++.h"
#define ALL(obj) (obj).begin(),(obj).end()
#define RALL(obj) (obj).rbegin(),(obj).rend()
#define REP(i, n) for(int i = 0; i < (int)(n); i++)
#define REPR(i, n) for(int i = (int)(n); i >= 0; i--)
#define FOR(i,n,m) for(int i = (int)(n); i < int(m); i++)
using namespace std;
typedef long long ll;
const int MOD = 1e9 + 7;
const int INF = MOD - 1;
const ll LLINF = 4e18;

int n;
vector<int> L;
ll k;

// 長さmの棒を作れるか
bool f(double m) {
    ll cnt = 0;
    REP(i, n) {
        cnt += int(L[i] / m);
    }
    if (cnt >= k) {
        return true;
    }
    return false;
}

int main() {
    cin >> n;
    L.resize(n);
    REP(i, n) cin >> L[i];
    cin >> k;
    double l = 0, r = 1e9+1;
    while (r - l > 1e-7) {
        double mid = r - (r - l) / 2;
        if (f(mid)) {
            l = mid;
        }
        else {
            r = mid;
        }
    }
    printf("%.10f", l);
    getchar(); getchar();
}