import java.util.Scanner;

class Main {
    public static void main(String[] args) throws Exception {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int a = n - 98;
        in.close();

        while(true) {
            //Fermat test
            if((Math.pow(2, (a-1)) % a) != 1) {
                System.out.println(a);
                break;
            } else {
                a++;
            }
        }
    }
}