import Control.Applicative ((<$>), (<*>))

main :: IO ()
main = solve <$> f <*> f >>= putStrLn
  where f = map read <$> words <$> getLine

solve :: [Int] -> [Int] -> String
solve [n, m] [x, y] | f (x-1) == f (y-1) = "YES"
                    | otherwise = "NO"
  where f i | even q = r
            | otherwise = m - 1 - r
          where (q, r) = divMod i m