it's 2 rows of number of a position that is 2 dimensional, and it's this column, again, is just a single column if our position is 1 dimensional; otherwise, it is 2 column, and we initialize those all by 0, and then we can apply our regular motion update, that as you know adds 1 or some number like 1 to the main diagonal and -1s off diagonal, and the same on the right side for the vector c.