loop do
  line = gets.chomp.split
  h = line[0].to_i
  w = line[1].to_i

  break if h == 0 && w == 0

  for i in 1..h
    for j in 1..w
      if (i+j) % 2 == 0
        print '#'
      else
        print '.'
      end
    end
    puts
  end

  puts
end