void display() {
        cout <<  "  1   2   3   4   5   6 " << endl;
        cout <<  " 1-----------------------2" << endl;

        cout << "A | " << quad[0][0] << "   " << quad[0][1] << "   " << quad[0][2] << " | ";
        cout <<           quad[1][0] << "   " << quad[1][1] << "   " << quad[1][2] << " | A" << endl;

        cout << "B | " << quad[0][3] << "   " << quad[0][4] << "   " << quad[0][5] << " | ";
        cout <<           quad[1][3] << "   " << quad[1][4] << "   " << quad[1][5] << " | B" << endl;

        cout << "C | " << quad[0][6] << "   " << quad[0][7] << "   " << quad[0][8] << " | ";
        cout <<           quad[1][6] << "   " << quad[1][7] << "   " << quad[1][8] << " | C" << endl;

        cout << "D | " << quad[2][0] << "   " << quad[2][1] << "   " << quad[2][2] << " | ";
        cout <<           quad[3][0] << "   " << quad[3][1] << "   " << quad[3][2] << " | D" << endl;

        cout << "E | " << quad[2][3] << "   " << quad[2][4] << "   " << quad[2][5] << " | ";
        cout <<           quad[3][3] << "   " << quad[3][4] << "   " << quad[3][5] << " | E" << endl;

        cout << "F | " << quad[0][6] << "   " << quad[0][7] << "   " << quad[0][8] << " | ";
        cout <<           quad[1][6] << "   " << quad[1][7] << "   " << quad[1][8] << " | C" << endl;

        cout << "  3-----------------------4 " << endl;
        cout << "   1   2   3   4   5   6 " << endl;
    }