defmodule Solution do
    def split_numbers(s) do
        String.split(s, " ")
        |> Enum.map(fn x -> Integer.parse(x) |> elem(0) end)
    end
    
    def find_by_k(list, k) do
        grouped = Enum.group_by(list, fn x -> x end)
        output = Enum.filter(list, fn x -> Enum.count(grouped[x]) >= k end)
        |> Enum.uniq
        if Enum.count(output) == 0 do
            [-1]
        else
            output
        end
    end
end



input = IO.read(:stdio, :all)
  |> String.split("\n")
  
[_ | elements] = input
Enum.chunk_every(elements, 2)
|> Enum.map(fn [config, list] -> 
    [_, k] = Solution.split_numbers(config)
    l = Solution.split_numbers(list)
    Solution.find_by_k(l, k)
end)
|> Enum.map(fn line ->
    IO.puts Enum.join(line, " ")
end)