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.math.*;
import java.util.*;
import java.lang.*;
import java.io.*;



	

public class CodeChef {



public static void main(String[] args) throws IOException {

	 BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringBuilder sb=new StringBuilder();
   long n=Long.parseLong(br.readLine());
long count=0;
boolean flag=false;
 while(n>0)
 {
	   
	   if(n%2==0)
	   { count+=n/2;break;}
	   
		   for(int i=3;i<=Math.sqrt(n)&&(n>0);i=i+2)
		   {
			   if(n%i==0)
			   {n=n-i;count++; flag=true;
				   break;
			   }
		   }
		   if(!flag)
		   {
			   n=0;count=1;
		   }
	   
	   
	   
	   
	   
	   
	   
   }
 System.out.println(count);
	

}
}