n = int(input())
L = list(map(int, input().split()))
k = int(input())
r = sum(L) + 1
l = 0
for _ in range(300):
    c = (r + l) / 2
    cnt = sum(li // c for li in L)
    if cnt >= k:
        l = c
    else:
        r = c
print(l)