#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MOD = 1000000007;
const int MAX_N = 200010;
const int INF = 1000000010;

#define REP(i,n) for((i)=0;(i)<(int)(n);(i)++)

int n, k;
int l[MAX_N];

bool C(double x){
    ll sum = 0;
    for (int i = 0; i < n; i++) sum += (ll)(l[i] / x);
    return sum >= k;
}

int main(){
    cin >> n;
    for (int i = 0; i < n; i++) cin >> l[i];
    cin >> k;

    double ok = 0;
    double ng = INF;
    for (int i = 0; i < 100; i++){
        double mid = (ok + ng) / 2;
        if (C(mid)) ok = mid;
        else ng = mid;
    }

    printf("%.15f\n", ok);

    return 0;
}