
arr = []

while true
  h, w = gets.split(" ").map(&:to_i)
  break if h.zero? && w.zero?
  arr << [ h, w ]
end

value = "#"
arr.each do |array|
  str = ""
  array[0].times do |ind1|
    ind1 += 1
    array[1].times do |ind2|
      ind2 += 1
      if value == "#"
        if ind2.odd?
          str += "#"
        else
          str += "."
        end
      else
        if ind2.odd?
          str += "."
        else
          str += "#"
        end
      end
    end

    if value == "#"
      value = "."
    else
      value = "#"
    end
    str += "\n"
  end
  value = "#"
  puts str
  puts "\n"
end