def rec(h,w)
  h.times do |x|
    w.times do |y|
      if (x + y) % 2 == 0
        print '#'
      else
        print '.'
      end
    end
    print "\n"
  end
end

while true
  h, w = gets.chomp.split.map(&:to_i)
  break if w == 0 && h == 0
  rec(h, w)
  puts ""
end

