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.BufferedReader;
import java.io.InputStreamReader;
import java.util.*;

public class B {

    private void work() {
        Scanner sc = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
        long n = sc.nextLong();
        sc.close();

        if (n % 2 == 0) {
            System.out.println(n / 2);
            System.exit(0);
        }

        boolean[] isp = new boolean[100010];
        Arrays.fill(isp, true);
        for (int i = 2; i * i < isp.length; i++) {
            if (isp[i]) {
                for (int j = i * i; j < isp.length; j += i) {
                    isp[j] = false;
                }
            }
        }

        List<Long> ps = new ArrayList<>();
        for (int i = 2; i < isp.length; i++) {
            if (isp[i]) ps.add((long) i);
        }

        long res = 0;
        for (long p : ps) {
            if (p * p > n) break;
            if (n % p == 0) {
                res = 1 + (n - p) / 2;
                break;
            }
        }
        if (res == 0) res = 1;

        System.out.println(res);
    }

    public static void main(String[] args) {
        new B().work();
    }
}
