#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

#define rep(i,n) for(int i=0; i<n; i++)
#define all(x) (x).begin(),(x).end()
#define INF (1000000000)
#define MOD (1000000007)

int N,K;
double L[200010];

bool C(double x){//長さxの紐をK本作れるか
  int ret = 0;
  rep(i,N){
    ret += floor(L[i]/x);
  }
  return ret >= K;
}
int main(){
  cin >> N;
  rep(i,N){
    cin >> L[i];
  }
  cin >> K;

  double ok = 0, ng = 1000000000;
  while(!(ng-ok <= 1e-12 || ng-ok <= ok*1e-12)){
    double mid = (ok+ng)/2;
    if(C(mid)){
      ok = mid;
    }else{
      ng = mid;
    }
  }
  cout << fixed << setprecision(12) << ok << endl;
}