import math
N=int(input())
LN=list(map(float,input().split()))
K=int(input())

def isOK(len):
     cnt=0
     for i in LN:
          cnt+=math.floor(i/len)
     if cnt>=K:
          return True
     else:
          return False

ok=0
ng=10**9+1

while abs(ok-ng)>10**-11:
     mid=(ok+ng)/2.0
     if isOK(mid):
          ok=mid
     else:
          ng=mid

print(ok)