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

typedef long long ll;

bool enough(double x, vector<int> l,ll K){
    ll sum=0;
    for(int i=0;i<l.size();i++){
        sum+=(int) (l[i]/x);
    }
    return sum>=K;
}

int main(){
    int N;
    cin >> N;
    vector<int> l(N);
    for(int i=0;i<N;i++){
        cin >> l[i];
    }
    ll K;
    cin >> K;
    double left=0;
    double right=1000000000;
    int i=100;
    while(i--){
        double mid=(right+left)/2;
        if(enough(mid,l,K)){
            left=mid;
            //cout << left << endl;
        }else{
            right=mid;
            //cout << right << endl;
        }
    }
    printf("%.10f",left);
}