import Control.Applicative ((<$>), (<*>))
import Control.Monad (replicateM)

import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as B

import Data.List (unfoldr, foldl')
import Data.Char (isSpace)
import Data.Map (Map)
import qualified Data.Map as M

import Data.IntSet (IntSet)
import qualified Data.IntSet as IS

main :: IO ()
main = do
  [n, m, _] <- f
  solve n <$> replicateM m f <*> f >>= mapM_ putStrLn
  where f = readil B.readInt <$> B.getLine

solve :: Int -> [[Int]] -> [Int] -> [String]
solve n fts fs = let ls = foldl' (g mp) (IS.fromList [1..n]) fs in [(show . IS.size) ls, (unwords . map show . IS.toList) ls]
  where f mp [a, b, c] = M.insertWith (++) (a, c) [b] (M.insertWith (++) (b, c) [a] mp)
        mp = foldl' f M.empty fts
        g mp st d = IS.foldl' h IS.empty st
          where h s p = case M.lookup (p, d) mp of
                         Just xs -> IS.union s (IS.fromList xs)
                         Nothing -> s

readil :: Integral a =>  (ByteString -> Maybe (a, ByteString)) -> ByteString -> [a]
readil f = unfoldr g
  where
    g s = do
      (n, s') <- f s
      return (n, B.dropWhile isSpace s')