N = int(input())
L = list(map(int, input().split()))
K = int(input())

L.sort()

l = L[-1] / K
r = L[-1] + 1

for _ in range(60):
    m = l + r / 2
    n = sum(int(l / m) for l in L)
    if n >= K:
        l = m
    else:
        r = m

print((l + r) / 2)