import Control.Applicative
import Control.Monad
import qualified Data.ByteString.Char8 as B
import Data.Maybe (fromJust)
import Data.List
import Text.Printf
import Debug.Trace

-- or readInteger
readInts :: B.ByteString -> [Int]
readInts = map (fst . fromJust . B.readInt) . B.words

getInts :: IO [Int]
getInts = liftM readInts B.getLine

main = do
  [n] <- getInts
  xs <- getInts
  print $ solve $ Data.List.sort xs
  where
    solve xs = sub xs 0 2
    sub [] _ c = to c
    sub (x:xs) a c = if x == a then sub xs a (c+1)
                     else to c + sub xs x 1
    to c = if c > 1 then 0 else 1