loop {
  h, w = gets.split(" ").map(&:to_i)
  if h == 0 && w == 0
        break
  end
  for n in 1..h
    if (n%2) == 1
      for n in 1..h
        i = 0
          while i < (w-1)
            print "#"
            i += 1
            print "."
            i += 1
          end
          if (w%2) == 1
            puts "#"
          end
          i = 0
      end
      puts "\n"
    else
      for n in 1..h
        i = 0
        while i < (w-1)
          print "."
          i += 1
          print "#"
          i += 1
        end
        if (w%2) == 1
          puts "."
        end
        i = 0
      end
      puts "\n"
    end
  end
  puts "\n"
}