#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    ll n, k;
    cin >> n;
    double a[n];
    rep(i,n) cin >> a[i];
    cin >> k;
    double l = 0, r = 1001001001001001;
    rep(_,100){
        double m = (l + r) / 2;
        ll cnt = 0;
        rep(i,n){
            cnt += (ll)(a[i]/m);
        }
        if(cnt >= k) l = m;
        else r = m;
    }
    cout << fixed << setprecision(10) << l << endl;
    return 0;
}