Tabitha writes down a four-digit number $$N$$.  She then rubs out one of the digits and creates a new three-digit number, $$M$$, with the three digits that are left (in the same order as before).  The difference between $$N$$ and $$M$$ is 2021.  What is Tabitha\textquotesingle s original number $$N$$? 
Overseas Competition->Knowledge Point->Combinatorics->Number Puzzles->Number Puzzles (horizontal forms)