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.*;
import java.io.*;
public class a{
    static Scanner sc=new Scanner(System.in);
   static  boolean isPrime(long n){
        for(long i=2;i*i<=n;i++){
            if(n%i==0)return false;
        }
        return true;
    }
   static long smf(long n){
       for(long i=3;i*i<=n;i++){
           if(n%i==0){
               return i;
           }
       }
       return -1;
   }
    public static void main(String [] args){
        long n=sc.nextLong();
        long ans=0;
        if(n%2==0){
            ans=n/2;
        }
        else{

            if(isPrime(n)){
                ans=1;
                // System.out.println("prime");
            }
            else{

                n=n-smf(n);
                ans=1+(n/2);
            }
        }

        System.out.println(ans);

    }
}