def INPUT():
	n=int(input())
	l=list(map(int,input().split()))
	k=int(input())
	return n,l,k

def ok(mid,n,l,k):
	cnt=0
	for i in range(n):
		cnt+=l[i]//mid
	return cnt>=k

def solve(n,l,k):
	ub,lb=[max(l),0]
	for i in range(60):
		mid=(ub+lb)/2
		if ok(mid,n,l,k):
			lb=mid
		else:
			ub=mid
	return lb

def main():
	n,l,k=INPUT()
	print("{:.20}".format(solve(n,l,k)))

if __name__=="__main__":
	main()