import java.util.*;

public class Main {
	
	public static void main(String[] args) {
		Scanner sc=new Scanner (System.in);
		int n=sc.nextInt();
		int L[]=new int[n];
		for(int i=0;i<n;i++){
			L[i]=sc.nextInt();
		}
		long k=sc.nextLong();
		
		double min=0;
		double max=1000000000;
		double mid=0;
		int p=0;
		while(p<200){
			mid=(min+max)/2;
			long sum=0;
			for(int i=0;i<n;i++){
				sum+=L[i]/mid;
			}
			if(sum>=k)min=mid;
			else max=mid;
			p++;
		}
		System.out.println(mid);
	}}