from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline


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

def is_ok(x):
    
    tmp = 0
    for l in L:
        tmp += l//x
        
    return tmp>=K
    
x = 0.001
y = 10**10
while y-x>0.000000001:
    mid = (y+x)/2
    if is_ok(mid):
        x = mid
    else:
        y = mid
print(x)