ACMKANPA problem (detecting knots on a string)

Does anybody knows if it is possible to have any information about this problem? It’s in the practice -> hard section. I’ve made some submission which wheren’t accepted and since many others also did, I wonder if it is possible to have some extra info about the problem itself, the test cases used to validate the solution or the errors on the code submitted (ie: the python traceback)… I believe a problem that got no valid solution for 3 years could be tricky to solve with no hits! Regards