def addCell(j, str)
  j % 2 == 0 ? str + "." : str + "#"
end

loop do
  h, w = gets.split.map!(&:to_i)
  break if h == 0 && w == 0
  h.times do |i|
    pattern = ""
    w.times do |j|
      pattern = addCell(i % 2 == 0 ? j : j + 1, pattern)
    end
    puts pattern
  end
  puts ""
end