N = int(input())
L = tuple(map(int, input().split()))
K = int(input())
l, r = 0, 10 ** 9

while r - l > 10 ** -10:
    m = (l + r) / 2
    if sum(int(l // m) for l in L) < K:
        r = m
    else:
        l = m
print(l)