题解 | #杨辉三角的变形#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int a = in.nextInt();

            if (a <= 2) {
                System.out.println(-1);
                continue;
            }

            int r = a % 4;
            int out = -1;
            switch (r) {
                case 3:
                    out = 2;
                    break;
                case 0:
                    out = 3;
                    break;
                case 1:
                    out = 2;
                    break;
                case 2:
                    out = 4;
                    break;
            }
            System.out.println(out);
        }
    }
}