N = int(input())
L = list(map(int,input().split()))
K = int(input())
l = 0
r = sum(L)/K
while r-l >10**(-10):
    mid = (l+r)/2
    flag = True
    ans = 0
    for num in L:
        ans += num//mid
        if ans >= K:
            flag = False
            break
    if flag:
        r = mid
    else:
        l = mid
print(l)