gammaman

Say I have a digraph with any given number of nodes and I am told to find the path matrix of exactly length 3. What exactly does this mean? I know the matrix is represented as a 2D array of size n x n, depending on the number of nodes in the digraph. I also know that R3(path length 3) = R * R * R. So if anyone could please respond as to what is meant by an exact path matrix length and possibly show an example, that would be great.