N = int(input())
L = list(map(int,input().split()))
K = int(input())
eps = 1e-10
high = sum(L)/K+5
low = eps
while (high-low>eps) and (high-low)/high>eps:
    mid = (high+low)/2
    cnt = 0
    for i in range(N):
        cnt += L[i]//mid
    if cnt>=K:
        low = mid
    else:
        high = mid
print(high)