#include "bits/stdc++.h"
using namespace std;

int main(){
	int N;
	cin >> N;
	vector<int> L(N);
	for(int i = 0; i < N;i++){
		cin >> L[i]; 
	}
	long long K;
	cin >> K;

	double low = 0;
	double high = 1e9;
    for(int t = 0;t < 100;t++){
    	double mid = (low + high)/2;
    	long temp = 0;
    	for(int i = 0;i < N;i++){
    		temp += (long long)(L[i] / mid);
    	}
    	if(temp >= K) low = mid;
    	else high = mid;
    }
    printf("%.14f\n",low);
}