/ This is my first post on codeforces, so I apologize for the quality. In the last 1004th round, I tilted hard because of Task A. I think there's a mistake in the tesas here. Can someone explain me why I got WA in test case 2. There was x = 1 and y = 9. So if we take n=9 S(9)=9 and S(n+1)=S(10)=1, and the answer is YES.