def chess(arr)
	arr.each{|i|
		count = 1
		1.upto(i[0]){
			line = ""
			if (count % 2 == 1)
				cnt = 1
				1.upto(i[1]){
					if (cnt % 2 == 1)
						line << "#"
					else
						line << "."
					end
					cnt += 1
				}
				puts line
				count += 1
			else
				cnt = 1
				1.upto(i[1]){
					if (cnt % 2 == 1)
						line << "."
					else
						line << "#"
					end
					cnt += 1
				}
				puts line
				count += 1
			end
		}
		puts ""
	}
end


input_arr = []
while input = gets
	h, w = input.split(' ').map(&:to_i)
	break if (h == 0 && w == 0)
	input_arr << [h, w]
end

chess(input_arr)