Difficulty level

Those 2 tests that you added are absolutely not difficult. They are exactly the same as the previous ones. But they revealed some mistakes, it's good too.

For those who want complexity, you can add any matrix 5x5 with path in the range 18-20. If someone's function survives, then it will be 1-2 people on both sites. I described this problem in my solution.

// Hardly processes path > 12, e.g. for path = 15 the number of possible paths is 3593532. 
// Starting with path = 21, you can simply select the maximum values, 
// because the path through them can always be laid.