module Main where

import qualified Data.Array as A

main ::  IO ()
main = do size <- fmap read getLine :: IO Int
          tree <- fmap (map read . words) getLine :: IO [Int]
          let m = A.listArray (0, size) $ map (\x -> if x == -1 then 0 else 2 + fun1 (a A.! x)) tree
              a = A.listArray (0, size) tree
              fun1 i = if i == -1 then 1 else m A.! i
          print $ maximum $ map fun1 tree