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

def summery(L, d):
    n = 0
    for i in L:
        n += int(i / d)
    return n

low = 0
high = max(L) + 1
mid = (low + high) / 2.0
while abs(low - high) / mid > 10**(-9):
    mid = (low + high) / 2.0
    if summery(L, mid) >= K:
        low = mid
    else:
        high = mid
    
print(low)