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.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.*;
import java.io.*;
public class j19 {
    public static void main(String[] args) throws Exception{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      long n = Long.parseLong(br.readLine());
      if(prime(n)){
          System.out.println("1");
      }
      else{
          if(n%2 == 0){
              System.out.println(n/2);
          }
          else{
              System.out.println("2");
          }
      }
    }
  public static boolean prime(long n){
       int count = 0;
       for(long i=1;i*i<=n;i++){
           if(n%i == 0){
               count += 2;
               if(i*i == n){
                   count--;
               }
           }
       }
       if(count == 2){
           return true;
       }
       return false;
   }
}