Walk on the Grid

There is a grid of size R×CR\times CR×C where R=R = R= Number of rows and C=C = C= Number of columns. You shall walk on the grid and you can only move from (X,Y)(X,Y)(X,Y) cell to (X+1,Y)(X+1,Y)(X+1,Y) or (X,Y+1)(X,Y+1)(X,Y+1) cell. You shall walk exactly LLL cells on the way.

This is a companion discussion topic for the original entry at https://toph.co/p/walk-on-the-grid