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.*;
public class Main{
    public static void main(String args[]){
        class bc{
        boolean isPrime(long num){
            boolean flag = true;
            for(int i=2;i<=num/2;++i){
                if(num%i==0){
                    flag = false;
                    break;
                }
            }
            return flag;
        }
    }
        Scanner sc = new Scanner(System.in);
        bc c = new bc();
        long n,d=0,i;
        n = sc.nextLong();
        if(c.isPrime(n)){
            System.out.println("1");
        }
        else{
            if(n%2 == 0)System.out.println(n/2);
            else{
                for(i=2;i<n;i++){
                    if(n%i == 0){d = i;break;}
                }
                try{
                    System.out.println(n/d);
                }
                catch(Exception e){System.out.println(e);}
            }
        }
    }
}