import sys,math,collections,itertools
from collections import deque
INF = 10**18
def I(): return int(input())
def MI(): return map(int,input().split())
def LI(): return list(map(int,input().split()))
def TI(): return tuple(map(int,input().split()))
def S(): return input()
def LS(): return list(input().split())
def TS(): return tuple(input().split())
def lcm(a, b): return a * b // math.gcd(a, b)
MOD1 = 10**9+7 #500000004
MOD2 = 998244353 #499122177
sys.setrecursionlimit(10**9)

a = I()
l = LI()
k = I()
m = 10**(-9)
M = 10**9
for i in range(100):
    mid = (m+M)/2
    s = 0
    for j in range(a):
        s += l[j]//mid
    if s >= k:
        m = mid
    else:
        M = mid
print(m)