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.*;
import java.lang.reflect.Array;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Solution {
    
    private static final Scanner sc = new Scanner(System.in);

    public static void main(String[] args) throws IOException {
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        //StringTokenizer st = new StringTokenizer(br.readLine());
        long n = sc.nextLong();
        if (n%2 == 0){
            System.out.println(n/2);
            return;
        }
        for (int i=3; i<=Math.sqrt(n); ++i){
            if (n%i == 0){
                n-=i;
                n = n/2;
                n+=1;
                System.out.println(n);
                return;
            }
        }
        System.out.println(1);
        sc.close();
        br.close();
        bw.close();
    }
    
}
