n=int(input())
al=list(map(int,input().split()))
k=int(input())
def zen(x):
	ans=0
	for i in al:
		if i>=x:ans+=i//x
	return ans
	
ok,ng=0,10**10+1
while(ng-ok>=10**-12):
	mid=(ok+ng)/2
	if zen(mid)>=k:ok=mid
	else:ng=mid
print(ok)