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.
import java.util.*;
public class DivisorSubtraction {
    public static void main(String args[])
    {
        long i,j,n,k,sq,idx=0,t,count=0;
        Scanner sc=new Scanner(System.in);
        long sum=0;
        long flag=0;
        n=sc.nextLong();
        while(n!=0)
        {
            flag=0;
            sq=(long)Math.ceil(Math.sqrt(n));
            for(i=2;i<=sq;i++)
            {
                if(n%i==0)
                {
                    idx=i;
                    flag=1;
                    break;
                }
            }
            if(flag==1)
            {
                if(idx==2)
                {
                    count=count+n/2;
                    break;
                }
                n=n-idx;
                count++;
            }
            else{
                n=n-n;
                count++;
            }
        }
        System.out.println(count);
    }
}
