line = "#." * 151

loop do
  h, w = gets.chomp.split(" ").map(&:to_i)
  break if h == 0 && w == 0
  h.times do |i|
    if i % 2 == 1 then
      puts line[1..w]
    else
      puts line[0..w-1]
    end
  end
  puts ""
end