Interactive problems are where the input given to your programs changes based on the programs response. This means that in most common competitve programming setups, the only option left is to manually interact with your solution program to check if it's correct.

However in most cases the checker programs(programs which check your program's correctness) are easy to write. The only difficulty is in getting the checker program to interact with you solution program.

There are already solutions to this, the one over here uses croupier(a python program) to make the two interact.

However, if you have access to a linux terminal you can actually solve this problem way more easily. mkfifo pipe_in