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.
/*
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 * and open the template in the editor.
 */

import java.util.*;

/**
 *
 * @author arvin
 */
public class divisor_sub {
    public static void main(String args[])
    {
        Scanner sc=new Scanner(System.in);
        long n=sc.nextLong();
        long prime=0l;
        int flag=0;
        for(long i=2l;i<=Math.sqrt(n);i+=2)
        {
            if(n%i==0)
            {
                prime=i;
                flag=1;
                break;
            }
        }
        if(flag==0)
            prime=n;
        long count=1l;
        n-=prime;
        count+=(n/2);
        System.out.println(count);
    }
}
