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

typedef long long ll;

int ok( const vector< int > &stick, ll k, double len ){
  for( int i = 0; i < stick.size(); ++i )
    k -= floor( 1.0 * stick[ i ] / len );
  return k <= 0;
}

signed main(){
  int N; cin >> N;
  vector< int > L( N );
  for( int i = 0; i < N; ++i )
    cin >> L[ i ];
  ll K; cin >> K;
  double lb = 0.0, rb = *max_element( L.begin(), L.end() );
  for( int i = 0; i < 100; ++i ){
    double mid = ( lb + rb ) / 2;
    if( ok( L, K, mid ) )
      lb = mid;
    else
      rb = mid;
  }
  cout << fixed << setprecision( 10 ) << lb << endl;
  return 0;
}