In The Upside Down

Through some mysterious circumstances, Eleven is transported to the Upside Down, a parallel world filled with monsters. She wakes up and finds herself in a huge maze. She observes that the maze is shaped like a grid with m rows and n columns. She starts off initially at the position `(0, 0)`. She spots a portal at `(m-1, n-1)` which is the bottom right corner of the grid. She wants to find the s