#include <iostream>
#include <algorithm>
using namespace std;
using i64 = long long;

class range {private: struct I{int x;int operator*(){return x;}bool operator!=(I& lhs){return x<lhs.x;}void operator++(){++x;}};I i,n;
public:range(int n):i({0}),n({n}){}range(int i,int n):i({i}),n({n}){}I& begin(){return i;}I& end(){return n;}};

int main(void) {
  int n; scanf("%d", &n);
  vector<i64> l(n);
  for(int i : range(n)) { scanf("%lld", &l[i]); }
  i64 k; scanf("%lld", &k);
  double lo = 0., hi = *max_element(l.begin(), l.end());
  for(int times : range(300)) {
    double md = (lo + hi) / 2;
    i64 tmp = 0;
    for(int i : range(n)) {
      tmp += i64(l[i] / md);
    }
    if(tmp < k) {
      hi = md;
    } else {
      lo = md;
    }
  }
  printf("%lf\n", lo);
  return 0;
}