#coding: utf-8
#yuki67

n=int(raw_input())
ll=map(int,raw_input().split())
k=int(raw_input())

EPS=1e-9
l=0.0
r=10000000000
while l+EPS<r and l*(1.0+EPS)<r:
 m=(l+r)/2.0
 sum=0.0
 for i in xrange(n):
  sum+=ll[i]//m
 if sum<k:
  r=m
 else:
  l=m
   
print (l+r)/2