{-# LANGUAGE OverloadedStrings #-}
module Main where

import           Data.List
import           Control.Monad
import           Debug.Trace
import qualified Data.ByteString.Char8         as BC
import           Data.Maybe                     ( fromJust )
import qualified Data.Set                      as S
import qualified Data.IntMap.Strict            as IM
import qualified Data.Map.Strict               as M
import           Data.Char
import Data.Bits


readTuple2 :: IO (Int, Int)
readTuple2 = do
    [a, b] <- map (fst . fromJust . BC.readInt) . BC.words <$> BC.getLine
    return (a, b)

readTuple3 :: IO (Int, Int, Int)
readTuple3 = do
    [a, b, c] <- map (fst . fromJust . BC.readInt) . BC.words <$> BC.getLine
    return (a, b, c)

readInt :: IO Int
readInt = fst . fromJust . BC.readInt <$> BC.getLine

readInts :: IO [Int]
readInts = map (fst . fromJust . BC.readInt) . BC.words <$> BC.getLine

split :: (a -> Bool) -> [a] -> [[a]]
split f [] = []
split f as =
    let (fo, la) = span f as
        las      = case la of
            [] -> []
            xs -> split f $ tail xs
    in  case fo of
            [] -> las
            xs -> xs : las



solve :: Int -> [[(Int, Int)]] -> Int
solve n testifies =  let
    possibilities = replicateM n [True, False]
    isTestifyTrue possible = and $ do
        (saidMan, oneTestifySet) <- zip [1..]  testifies
        if not $ possible IM.! saidMan then pure True
        else do
            (targetMan, kindOrNot) <- oneTestifySet 
            if possible IM.! targetMan then pure $ kindOrNot == 1 else
                pure $ kindOrNot == 0

    countTrue possible = length $ filter id possible
    in
    maximum $ (\p -> if isTestifyTrue (IM.fromList $ zip [1..] p) then countTrue p else -1) <$> possibilities
main = do
    n <- readInt
    testifies <- replicateM n $ do
        i <- readInt
        replicateM i readTuple2
    print $ solve n testifies




