import java.math.*;
import java.util.*;
 
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] tree = new int[n];
        double max=0;
        for(int i=0;i<n;i++){
        	int temp=sc.nextInt();
        	tree[i]=temp;
        	max=Math.max(temp,max);
        }
        long k = sc.nextLong();
        double min=0;
        while(min<=max){
        	double temp=(min+max)/2;
        	long count=0;
        	for(int i=0;i<n;i++){
        		count+=(long)tree[i]/temp;
        	}
        	if(count>=k){
        		min=temp+0.00000001;
        	}else{
        		max=temp-0.00000001;
        	}
        }
        System.out.println(max);
    }
}