#include <stdio.h>

int n;
int L[200000];
long long int k;

int p(double x){
  long long int c = 0;
  int i;
  for(i=0;i<n;i++){
    c += (int) (L[i] / x);
  }
  return c >= k;
}

int main(){
  int i;
  long long int s = 0;
  double lb, ub;
  scanf("%d", &n);
  for(i=0;i<n;i++){
    scanf("%d", L+i);
    s += L[i];
  }
  scanf("%lld", &k);

  ub = s/k+1;
  lb = 0;

  while((ub-lb)*(1ULL<<32) > ub){
    double m = (lb + ub) / 2;
    if(p(m)) lb = m;
    else ub = m;
  }

  printf("%.20f\n", lb);

  return 0;
}