#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
const ll MOD=1000000007;
const ll INF=1000000010;
const ll LINF=4000000000000000010LL;
const int MAX=310;
const double EPS=1e-9;
int dx[4]={0,1,0,1};
int dy[4]={0,0,1,1};
double l[200010];
int main(){
	int n;cin>>n;
	for(int i=0;i<n;i++)cin>>l[i];
	ll k;cin>>k;
	double ok=0;double ng=INF;
	int cc=100;
	while(cc--){
		double mid=(ng+ok)/2;
		ll c=0;
		for(int i=0;i<n;i++){
			c+=floor(l[i]/mid);
		}
		if(c>=k){
			ok=mid;
		}else{
			ng=mid;
		}
	}
	printf("%.11f\n",ok);
    return 0;
}