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.util.*;

public class C {

    static long[] degs;

    public static void main(String[] args) {

        try (BufferedReader reader = new BufferedReader(new InputStreamReader(System.in))) {

            long n = Long.parseLong(reader.readLine());
            long i = 2;
            for(; i < n; i++) {
                if(n % i == 0)
                    break;
            }
            println(n / i);

        } catch (IOException e) {
        }
    }

    static String reverse(String s) {
        String ans = "";
        char[] c = s.toCharArray();
        for(int i = s.length() - 1; i >= 0; i--) {
            ans += c[i];
        }
        return ans;
    }

    static long fac(int deg) {
        long ans = 1;
        for(int i = 2; i <= deg; i++) {
            ans *= i;
        }
        return ans;
    }

    static int r(int a, int b) {
        int ans = a / b;
        if(a % b != 0)
            ans++;
        return ans;
    }

    static void print(Object o) {
        System.out.print(o.toString());
    }

    static void println(Object o) {
        System.out.println(o.toString());
    }
}