tests = $stdin.gets.to_i

tests.times do

  string = $stdin.gets.chomp
  if string.length % 2 == 0
    middle = string.length / 2

    left = string[0..(middle - 1)]
    right = string[middle..(string.length - 1)]

    left_sort = left.chars.sort
    right_sort = right.chars.sort

    if left_sort == right_sort
      return 0
    else
      left_sort.each do |x|
        index = right_sort.index(x)
        right_sort.delete_at(index) unless index.nil?
      end
      puts right_sort.length
    end
  else
    puts -1
  end

end