N =int(input())
li =[int(i)for i in input().split()]
K =int(input())

def wa(L,d):
    n = 0
    for i in L:
        n += int(i/d)
    return n

def nibuntansaku(l,s):
    left = max(l)+1
    right =0
    while abs(right -left) > 10**(-10):
        mid = (left + right)/2.0
        if wa(l,mid) >= s:
            right =mid
        else:
            left =mid
    return right
print(nibuntansaku(li,K))