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

main :: IO ()
main = do
  solve <$> getl (map read .words) <*> getl (map read .words) >>= putStrLn

solve :: [Int] -> [Int] -> String
solve [n, a] xs = if n * a == sum xs then "YES" else "NO"

getl :: (String -> a) -> IO a
getl f = f <$> getLine