array = Array.new
while true
	a = gets.split(" ").map{|e|e.to_i}
	break if a[0] == 0 && a[1] == 0
	array.push a
end

array.each{|a|
	a[0].times{|a0|
		a[1].times{|a1|
			if (a0+a1)%2 == 0
				print "#"
			else
				print "."
			end
		}
		puts ""
	}
	puts ""
}