    array([[-1, -1, 19, -1],
           [-1, -1, 20, -1],
           [-1, -1, 21, -1],
           [-1, -1, 22, -1],
           [-1, -1, 23, 20],
           [-1, 19, 24, 21],
           [-1, 20, 25, 22],
           [-1, 21, 26, -1],
           [19, -1, -1, 24],
           [20, 23, -1, 25],
           [21, 24, -1, 26],
           [22, 25, -1, -1],
           [23, -1, -1, -1],
           [24, -1, -1, -1],
           [25, -1, -1, -1],
           [26, -1, -1, -1]])
