[VA] SRC #012a - Then and Now: Probability

[PeterP]

Valentin, while it feels out of my reach, it is nonetheless very intriguing as your puzzles always are. Please apologize my question as a burden on your time: we are looking for the probability that we are in the last row after S steps, correct? Not the probability that we can reach the last row in at most S steps?

For S = R - 1 as in the example that is identical, but for S > R one can reach the last row and then step away from it again.