#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <cstring>

using namespace std;



int main(){
   int N;
   cin >> N;
   long long L[N];
   for(int i=0;i<N;i++)cin>>L[i];
   long long K;
   cin >> K;
   double left=0;
   double right=1e9;
   while(left*(1+1e-10)<right&&left+1e-10<right){
      double mid=(left+right)/2;
      long long cnt = 0;
      for( int i = 0 ; i < N; i++ ){
         cnt += (long long)(L[i]/mid);
      }
      if( cnt >= K) {
         left = mid;
      }
      else{
         right = mid;
      }
   }

   printf("%.10f\n",left);
   return 0;
}