while n = gets.split.map(& :to_i)
  if n[0] == 0 && n[1] == 0
    break
  end
  n[0].times do |i|
    if i % 2 == 1
      n[1].times do |j|
        if j % 2 == 1
          print "#"
        else
          print "."
        end
      end
      puts ""
    else
      n[1].times do |j|
        if j % 2 == 1
          print "."
        else
          print "#"
        end
      end
      puts ""
    end
  end
  puts ""
end