I copied the code for the question 1811E from the gfg site of an almost similar question,and had to do minor change as per 1811E, the source code was published way before the contest. Im attaching the link of the gfg code i used for my soln.

https://www.geeksforgeeks.org/finding-the-nth-term-in-a-sequence-formed-by-removing-digit-k-from-natural-numbers/amp/

Thanks