You are given an integer number n. The following algorithm is applied to it:

  1. if n = 0, then end algorithm; 
  2. find the smallest prime divisor d of n; 
  3. subtract d from n and go to step 1. 



Determine the number of subtrations the algorithm will make.

Input

The only line contains a single integer n (2 ≤ n ≤ 10^{10}).

Output

Print a single integer — the number of subtractions the algorithm will make.

Examples

Input


5


Output


1


Input


4


Output


2

Note

In the first example 5 is the smallest prime divisor, thus it gets subtracted right away to make a 0.

In the second example 2 is the smallest prime divisor at both steps.
# coding=utf-8

import math

num = input()

ok = False
r = -1

for i in range(2, int(math.sqrt(num)) + 2):
    if num % i == 0:
        ok = True
        r = i
        break

if ok:
    print num / r
else:
    print 1
 				  			 	 	 	    				 	  			