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.Scanner;
import java.util.*;

public class Main
{


    public static void main(String args[]) {
//        Scanner in = new Scanner(System.in);
//        int length = in.nextInt();
//        String string = in.next();
//        int current = 1;
//        while(string.charAt(current) > string.charAt(current-1)){
//            current++;
//            if(current==length)break;
//        }
//        if(current == length){
//            System.out.println(string);
//        }
//        else {
//            System.out.println(string.substring(0,current-1) + string.substring(current,length));
//        }



        Scanner in = new Scanner(System.in);
        long n = in.nextLong();
if(n%2==0)
    System.out.println(n/2);
else{
    int count=0;
    while(n!=0){
        n-=getSmallest(n);
        count++;
        if(n%2==0){
            count+=n/2;
            break;
        }
    }
    System.out.println(count);
}

    }

    static long getSmallest(long x){
        for(long i =2;i<=x;i++){
            if(x%i==0) return i;
        }

        return 0;
    }
}

