A class is holding a maths competition and a coding competition. Every student is required to participate in at least one of them. There are $$36$$ students participating in the coding competition; $$21$$ students participating in the math competition and $$20$$ students participating in both. Find the total number of students in this class. 
Overseas Competition->Knowledge Point->Counting Modules->Inclusion-Exclusion Principle->Inclusion-Exclusion Principle for Two Sets Overseas Competition->Knowledge Point->Counting Modules->Permutations and Combinations->Combinations