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

def judge(l):
    cnt = 0
    for i in range(N):
        cnt += L[i]//l
    if cnt>=K:
        return True
    else:
        return False

ok, ng = 0, 10**10
while ng-ok>1e-10:
    mid = (ok+ng)/2
    if judge(mid):
        ok = mid
    else:
        ng = mid
print(ok)