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.
//package Contests.Round54;

import java.util.Scanner;

public class B_SubtractDivisor {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        long n = scanner.nextLong();
        long count = 0;
        int min_i = 2;
        boolean flag;

        while (n != 0){
            flag = true;
            for (int i = min_i; i < (int)Math.sqrt(n) + 1; i++) {
                if (n % i == 0){
                    long k = n / i;
                    n -= k*i;
                    min_i = i;
                    count += k;
                    flag = false;
                    break;
                }
            }
            if (n == 0){
                break;
            }
            if (flag){
                count++;
                break;
            }

        }
        System.out.println(count);
    }
}
