163120

PFA

I had seen this problem earlier, and partially knew the approach to this problem. In my country's math olympiad (IOQM, India) that happened just two months ago, there was one such question. Here is the link to the pdf, question 28: https://www.mtai.org.in/wp-content/uploads/2021/01/IOQM-question-paper…

Interestingly, such numbers were said to be "good" in that question, and in this problem, it was "polite". I guess the numbers that are powers of 2 are not really obedient, haha!