题解 | 数楼梯

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();
            System.out.println(climbCheck(a));
        }
    }


    public static int climbCheck(int num) {
        int left = 1, right = 2;
        for (int i = 3; i <= num; i++) {
            int tmp = right;
            right = (left + right)%998244353;
            left = tmp;
        }
        return right;
    }

}