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 CF1076;

import java.util.Scanner;

public class CF1076B {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        long m = s.nextLong();
        long ans;
        if (m % 2 == 0) {
            ans = m / 2;
        } else {
            long p = primeFactors(m);
            ans = (m - p) / 2 + 1;
        }
        System.out.println(ans);
    }

    public static long primeFactors(long n) {
        // Print the number of 2s that divide n

        while (n % 2 == 0) {
            return 2;
        }

        // n must be odd at this point.  So we can
        // skip one element (Note i = i +2)
        for (long i = 3; i <= Math.sqrt(n); i += 2) {
            // While i divides n, print i and divide n
            while (n % i == 0) {
                return i;
            }
        }

        // This condition is to handle the case whien
        // n is a prime number greater than 2
        if (n > 2)
            return n;

        return -1;
    }



}
