while true
  rect = gets.split.map(&:to_i)

  if rect[0] == 0 && rect[1] == 0
    break
  end

  for i in 1..rect[0] do
    if i % 2 == 0
        for j in 1..rect[1] do
            if j % 2 == 0
              print '#'
            else
              print '.'
            end
        end
            print "\n"
    else
        for j in 1..rect[1] do
              if j % 2 != 0
                print '#'
              else
                print '.'
              end
        end
            print "\n"
    end
  end
  print "\n"
end

