import Data.List
import Data.Ord
main = do
  t <- readLn :: IO Int
  xs <- fmap (map read . words) getLine :: IO [Int]
  print $ maximum $ map (flip g (f xs)) [minimum xs .. maximum xs]
    where
      f xs = map (\x -> (head x, length x)) $ group $ sort xs
      g n = foldl (\acc y -> acc + snd y) 0 . filter (\x -> fst x >= n - 1 && fst x <= n + 1)
