题解 | #杨辉三角的变形#

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = Integer.valueOf(scan.nextLine().trim());
        if (n == 1 || n == 2) {
            System.out.println(-1);
        } else if (n % 2 != 0) {
            System.out.println(2);
        } else {
            System.out.println(n / 2 % 2 == 0 ? 3 : 4);
        }
    }
}