import sys
input = sys.stdin.readline

n = int(input())
L = list(map(int, input().split()))
k = int(input())
eps = 1e-9

left = max(L) / k
right = sum(L) / k
for _ in range(100):
    mid = (left + right) / 2
    cnt = 0
    for i in range(n):
        cnt += int(L[i] / mid)
    if cnt >= k:
        left = mid
    else:
        right = mid
print(left)