{-# LANGUAGE LambdaCase #-}

import Data.List

count e [] = 0
count e (x : xs) = if x == e then 1 + count e xs else count e xs

byCount c l = nub $ filter (\e -> count e l >= c) l

readAllInts :: String -> [[Int]]
readAllInts = map (map read . words) . lines

showResults :: Show a => [[a]] -> String
showResults = unlines . map (unwords . map show)

takes c [] = []
takes c l = take c l : takes c (drop c l)

solve s = showResults $ map (\l -> if null l then [-1] else l) solutions
  where
    inputs = takes 2 . tail . readAllInts $ s
    solutions = map (\case [[_, c], l] -> byCount c l; _ -> []) inputs
    
main = interact solve