Don't know if it is allowed to ask for a hint, but I am stuck with this problem. Test data from example gives the right answer, but test data for which I need to find the answer gives a wrong one. I've tried using 1024-bit integer (from boost), taking modulo of all node values, but nothing has worked. My algorithm is straightforward -- it recursively traverses through all nodes calculating their values, and I can't understand what I am getting wrong here. Any advice will be appreciated.

Don't know if it is allowed to ask for a hint

I believe it's quite ok, just the matter whether someone could and want provide a hint :)

My algorithm is straightforward

generally problems created by Clive (aka CSFPython) may need some cunning, also they (unless I have forgotten something) never require using long arithmetics :)

take this for the first hint as I see with some surprise I solved it myself after some struggle, but can't remember the idea at once.

Code provided by Clive for data generator in this problem works in Python (which is 10-20 times slower compared to natively compiled C/C++) and seemingly does the trick in about a second.