题解 | 数楼梯

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt(), base = 998244353;
        int[] dp = new int[n + 1];
        for (int i = 1; i <= n; i++) {
            if (i < 3) dp[i] = i;
            else dp[i] = (dp[i - 1] + dp[i - 2]) % base;
        }
        System.out.println(dp[n]);
    }
}