vector<vector<int>> ijkalgorithm(vector<vector<int>> A,
                                 vector<vector<int>> B) 
{
    int n = A.size();

    // initialise C with 0s
    vector<int> tmp(n, 0);
    vector<vector<int>> C(n, tmp);

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            for (int k = 0; k < n; k++) {
                C.at(i).at(j) += A.at(i).at(k) * B.at(k).at(j);
            }
        }
    }
    return C;
}