while line = gets.chomp
  h,w = line.split(" ").map{|x| x.to_i}
  if h==0 && w==0
    break
  end
  for i in 1..h do
    for j in 1..w do
      if (i+j)%2==0
        print "#"
      else
        print "."
      end
    end
    print "\n"
  end
  print "\n"
end
