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());
      long p = 0;
      for(int v=2;v<=100000;v++){
          if(n%v == 0){
              p = v;
              break;
          }
      }
      if(0 == p){
          System.out.println(1);
      }
      else if(n%2 == 0){
          System.out.println(n/2);
      }
      else{
          System.out.println(1+(n-p)/2);
      }
   }
}