module Main where

anySame :: Eq a => [a] -> Bool
anySame = f []
 where
  f seen (x : xs) = x `elem` seen || f (x : seen) xs
  f seen []       = False

main :: IO ()
main = do
  getLine
  l <- getLine
  let ll = map read $ words l :: [Int]
  putStrLn $ if anySame ll then "YES" else "NO"
