N = int(input())
L = list(map(lambda x: int(x) * 10 ** 10, input().split()))
K = int(input())


def solve(x):
    cnt = 0
    for l in L:
        cnt += l // x
    return cnt >= K


left = 0
right = 10 ** 20

while right - left > 1:
    mid = (right + left) // 2
    if solve(mid):
        left = mid
    else:
        right = mid - 1

print(left / 10 ** 10)