inputs = []

while true
  h, w = $stdin.readline.split(" ").map {|s| s.to_i }

  if h == 0 && w == 0
    break
  end

  inputs.push([h, w])
end

inputs.each do |h, w|
  (1..h).each_with_index do |y, i|
    if i % 2 == 0
      (1..w).each do |x|
        if x % 2 == 0
          print "."
        else
          print "#"
        end
      end
      puts
    else
      (1..w).each do |x|
        if x % 2 == 0
          print "#"
        else
          print "."
        end
      end
      puts
    end
  end

  puts
end

