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.IOException;
import java.io.InputStreamReader;

public class Main {

    public static void main(String[] arg) {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        try {
            long n = Long.parseLong(reader.readLine());
            long count = 0;
            if(n%2 !=0) {
                n -= Main.small(n);
                count++;
            }

            System.out.println(count + n/2);

        } catch (IOException e) {
            e.printStackTrace();
        }


    }

    public static Long small(Long n) {
        for(long i=2;i*i<=n;i++) {
            if(n%i==0) return  i;
        }
        return  n;
    }
}
