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