import Data.List

main = do
 getLine
 nrs <- map ((\xs -> (map read (init xs), last xs)) . words) . lines <$> getContents
 print (kazuate nrs)

kazuate = head . foldr guess [0..9]
 where
  guess (ns,"YES") acc = intersect ns acc
  guess (ns,"NO") acc = acc \\ ns