while true
	h, w = gets.split( " " ).map { | val | val.to_i }
	break if 0 == h && 0 == w

	for i in ( 0 ... h ) 
		for j in ( 0 ... w )
			if 0 == (i+j)%2
				print( "#" )
			else
				print( "." )
			end
		end
		print( "\n" )
	end
	print( "\n" )
end