import Control.Applicative
import Data.List
import Data.Char

getInt :: IO Integer
getInt = (\a -> read a :: Integer) <$> getLine

getIntArray :: IO [Integer]
getIntArray = ((map (\a -> read a :: Integer)) . words) <$> getLine

getStrArray :: Integer -> IO [String]
getStrArray 0 = return [] :: IO [String]
getStrArray n = (:) <$> getLine <*> (getStrArray (n - 1))

check :: String -> Bool
check "" = False
check [_] = False
check [_, _] = False
check [_, _, _] = False
check ('L':'O':'V':'E':_) = True
check (_:rst) = check rst

main = do
    [n , _] <- getIntArray
    a <- getStrArray n
    putStrLn $ if any (\b -> check b) a then "YES" else "NO"