i = 0
while true do
  h,w = gets.split(" ").map(&:to_i)
  
  if h == 0 || w == 0 then
    break
  end

  h.times do |j|
    if j % 2 == 0 then
      w.times do |i|
        if i % 2 == 0 then
          printf("#")
        elsif
          printf(".")
        end
        i = i + 1
      end
    elsif
      w.times do |i|
        if i % 2 == 0 then
          printf(".")
        elsif
          printf("#")
        end
        i = i + 1
      end
    end
    puts("\n")
  end
end