Walter White and His Crystals

Walter White is trying to expand his area for selling his crystals. But Jesse tells him that the city whose name contains 'x' ( small letter 'x') is not safe to sell. Walter and Jesse appoint Shailesh to find if the area is safe, as they are busy cooking crystals. But Shailesh is not capable of doing this work, so he needs your help. You will be given a city name $S$, you have to tell whether i