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 B3 {
    public static void main(String[] args) throws IOException {
        try (BufferedReader br = new BufferedReader(new InputStreamReader(System.in))) {
            String firstLine = br.readLine();

            long startElement = Long.valueOf(firstLine);

            long result = -1;

            for (int i = 2; i <= (startElement+1)/2; i++) {
                if (startElement % i ==0) {
                    result = startElement/i;
                    break;
                }
            }

            if (result == -1) {
                System.out.println(1);
            } else {
                System.out.println(result);
            }
        }
    }
}
