while s=gets.split
  break if s==['0','0']
  h,w=s.map(&:to_i)
  (1..h).each{|i| (1..w).each{|j|
    if i%2==0
      print j%2==0 ? "#":"."
    else
      print j%2==0 ? ".":"#"
    end
    }
    puts
  }
  puts
end