#include <stdio.h>

int main() {
  int N, K;
  int L[200000];
  scanf("%d", &N);
  for (int i = 0; i < N; i++) {
    scanf("%d", &L[i]);
  }
  scanf("%d", &K);

  double EPS = 0.0000000001;
  double high = 1000000000;
  double low = 0.0;
  double middle;
  int sum;

  while (high-low > EPS) {
    middle = (high+low)/2.0;
    sum = 0;
    for (int i = 0; i < N; i++)
      sum += (int)(L[i]/middle);
    if (sum >= K)
      low = middle;
    else
      high = middle;
  }

  printf("%.09f", high);
  return 0;
}