Write a method uniqueRoutes to
find the total number of possible unique routes
for a mouse to walk from the top-left corner to the bottom-right corner of a grid.
The mouse is located at the top-left corner of a rowsxcols grid. It can only go either right or down at any point of time.

Try to solve this problem using dynamic programming.
Examples: uniqueRoutes(4,5) ==> 35