我已經拿遞歸AC了，對拍了一下也是全對，爲什麼用矩陣乘法最後四個點就是過不了？

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

struct matrix{
    int v[2][2];
    matrix(){
        memset(v, 0, sizeof v);
    }
    matrix operator*(matrix b){
        matrix c;
        for (int i = 0; i < 2; i++){
            for (int j = 0; j < 2; j++){
                for (int k = 0; k < 2; k++){
                    c.v[i][j] += v[i][k] * b.v[k][j];
                    c.v[i][j] %= 7654321;
                }
            }
        }
        return c;
    }
}ans, x;

void pm(int tmp){
    while (tmp > 0){
        if (tmp & 1) ans = ans * x;
        x = x * x; tmp >>= 1;
    }
}
int n;
int main(){
    x.v[0][0] = 1, x.v[1][0] = 1, x.v[0][1] = 1; ans.v[0][0] = 1;
    cin >> n;
    pm(n);
    cout << ans.v[0][1] % 7654321 << endl;
    return 0;
}