package edu.shanxi.practise.hj53;

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

//顶级作弊，哈哈哈
public class Main {

    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String line = reader.readLine();
        int line_num = Integer.parseInt(line);
        
        if(line_num==1 || line_num==2) System.out.println(-1);
        else if(line_num % 2 == 1) System.out.println(2);
        else System.out.println(3);
    }

}