import Data.Bits
import Data.Char
import Data.List

main = do
  dat <- readFile "jurassic.in"
  mapM_ (pp.solve) $ parse dat

parse :: String -> [[Int]]
parse dat = f $ lines dat where
  f (sn:ls)
    | n == 0 = []
    | otherwise = map cvt cur : f rest
    where
      n = read sn
      (cur,rest) = splitAt n ls
  cvt = foldr (\x d -> bit (ord x - ord 'A') .|. d) 0

solve xs = f 0 (0,[]) (zip [1..] xs) where
  f b sel [] = if b == 0 then sel else (0,[])
  f b (l,ls) ((i,x):xs) = max (f b (l,ls) xs) (f (b `xor` x) (l+1,i:ls) xs)

pp (l,ls) = do
  print l
  putStrLn $ concat $ intersperse " " $ map show $ reverse ls