题解 | #小乐乐走台阶#

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);
        int n = in.nextInt();
        System.out.println(fun(n));
    }
    public static int fun(int a) {
        if (a == 1) {
            return 1;
        } else if (a == 2) {
            return 2;
        }
        return fun(a - 1) + fun(a - 2);
    }
}