from math import log2


def judge(x):
    cnt = 0
    for li in L:
        cnt += int(li / x)
    return cnt >= K


def main():
    ok = 1e-9
    ng = 10**9+1
    # 許容誤差
    error = 10**(-9)

    for _ in range(int(log2(abs(ok - ng)/error)) + 2):
        mid = (ok + ng) / 2
        if judge(mid):
            ok = mid
        else:
            ng = mid
    return ok


N = int(input())
*L, = map(int, input().split())
K = int(input())
print(main())