Harshil Forgot JS Command.

There is a boy named Harshil. He is very Interested in making projects in different domains. Once he was working on Vanilla JS Projects. But, He was new in learning JS. He tends to forget commands. But He had knowledge of what the command does when you show him that command. To Tackle this Problem he invented his own Numeric Search Engine. He alloted the programs the numberings from 1 to K and then stored them in set of modulo operators. Now he forgot one JS command that he required to Toggle the classes. He has approaching nature. He asks you to select a random number. You have to suggest him any number between 0 to K-1. Lets us consider that his program is in Set x, Help him to crop down his search only to set x.