洛谷P3390题矩阵快速幂模板提交Java代码一直RE

洛谷P3390题，矩阵快速幂模板题，Java代码本地调试没有问题，提交上去就是Runtime Error，有没有好心人帮忙解答一下~

链接：https://www.luogu.com.cn/problem/P3390

洛谷平台用的JDK8，不知道是不是不兼容~

我的代码：

import java.util.Scanner;

public class Main {

    public static final long mod = 1000000007;

    public static long[][] matrixMultiply(long[][] matrixA, long[][] matrixB) {
        int n = matrixA.length, p = matrixB.length, m = matrixB[0].length;
        if (p != matrixA[0].length)
            return null;
        long[][] ans = new long[n][m];
        for (int i = 0; i < n; i++)
            for (int j = 0; j < m; j++)
                for (int k = 0; k < p; k++)
                    ans[i][j] += (matrixA[i][k] % mod) * (matrixB[k][j] % mod) % mod;
        return ans;
    }

    public static long[][] fastMatrixPow(long[][] matrix, long k) {
        int len = matrix.length;
        long[][] res = new long[len][len];
        for (int i = 0; i < len; i++)
            res[i][i] = 1;
        while (k > 0) {
            if ((k & 1) == 1)
                res = matrixMultiply(res, matrix);
            matrix = matrixMultiply(matrix, matrix);
            k = k >> 1;
        }
        return res;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long k = sc.nextInt();
        long[][] matrix = new long[n][n];
        for (int i = 0; i < n; i++)
            for (int j = 0; j < n; j++)
                matrix[i][j] = sc.nextInt();
        sc.close();
        long[][] res = fastMatrixPow(matrix, k);
        for (int i = 0; i < n; i++) {
            if (i != 0)
                System.out.println("");
            for (int j = 0; j < n; j++)
                System.out.print(res[i][j] + " ");
        }
    }
}

参考别人的程序：https://blog.csdn.net/qq_45492531/article/details/105132517