题解 | #循环汉诺塔#

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
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) throws IOException {
        BufferedReader in =  new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(in.readLine());
        long AToB = 1;
        long AToC = 2;
        for (int i = 2; i <= n; i++) {
            long  preAToB = AToB;
            long  preAToC = AToC + AToC;
            AToB = (preAToC + 1) % 1000000007;
            AToC = (preAToC + preAToB + 2) % 1000000007;
        }
        System.out.println(AToB + " " + AToC);

    }
}