import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class prog {

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

        String s = br.readLine();
        int nr = Integer.parseInt(s);
        if (nr == 2) {
            System.out.println("1");
            return;
        }

        if ((nr == 3) || (nr == 4)) {
            System.out.println("2");
            return;
        }

        if (nr == 5) {
            System.out.println("4");
            return;
        }

        if (nr == 6) {
            System.out.println("0");
            return;
        }

        if (nr == 7) {
            System.out.println("6");
            return;
        }

        if (nr >= 8) {
            if (isPrime(nr)) {
                System.out.println(nr - 1);
            } else {
                System.out.println("0");
            }
            return;
        }



    }

    public static boolean isPrime(int nr) {
        int part = (int) Math.sqrt(nr) + 1;
        for (int i = 2; i <= part; i++) {
             if (nr % i == 0) {
                 return false;
             }

        }
        return true;
    }

}