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

l = L[0] / K
r = max(L) + 1

for _ in range(60):
    m = (l + r) / 2
    n = 0
    for l in L:
        n += int(l/m)
    if n >= K:
        l = m
    else:
        r = m

print((l + r) / 2)