#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>
#include <functional>
#include <limits>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <complex>

using namespace std;

#define INF (INT_MAX/3)
#define PI (2*acos(0.0))
#define EPS (1e-8)

typedef long long ll;
typedef unsigned long long ull;

int N;
ll K;

bool judge(double x, vector<ll> &L){
  ll num = 0;
  for(int i = 0; i < N; i++){
    num += (int)floor(L[i] / x);
  }
  return num >= K;
}

int main(){
  ios_base::sync_with_stdio(0);
  cin >> N;
  
  vector<ll> L(N);
  for(int i = 0; i < N; i++) cin >> L[i];
  cin >> K;
  
  double lb = 0.0, ub = 1e15;
  for(int i = 0; i < 100; i++){
    double mid = (lb + ub) / 2;
    if(judge(mid, L)) lb = mid;
    else ub = mid;
  }
  printf("%.16f\n", lb);
  return 0;
}