java 矩阵快速幂

import java.util.*;
public class Main{
    static int m ;
    public static void main(String[] args){
        Scanner input = new Scanner(System.in);
        int n = input.nextInt();
        m = input.nextInt();
        //1 1 2  3

        long[][] matrix = cal(n-1);
        // for(int i = 0 ; i < 3 ; i++){
        //     System.out.println(Arrays.toString(matrix[i]));
        // }
        long res = 0;
        for(int i = 0 ; i < 3 ; i++){
            res = (res + matrix[i][2]) % m;
        }
        System.out.println(res);

    }
    public static  long[][] cal(int n ){
        long[][] base = {{0,1,0},{1,1,1},{0,0,1}};
        long[][] res = {{1,0,0},{0,1,0},{0,0,1}};
        while(n > 0){
            if((n & 1) == 1){
                res = multi(res,base);
            }
            n = n >> 1;
            base = multi(base,base);
        }
        return res;
    }

    public static long[][] multi(long[][] A,long[][] B){
        long[][] res = new long[A.length][B[0].length];
        for(int i = 0 ; i < A.length ; i++){
            for(int j = 0 ; j < B[0].length ; j++){
                for(int k = 0 ; k < A[0].length ; k++){
                    res[i][j] = (res[i][j] + A[i][k] * B[k][j]) % m;
                }
            }
        }
        return res;
    }
}