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

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

    for i in range(200):
        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)


def main():
    solve()


if __name__ == '__main__':
    main()