while true
	h, w = gets.split( " " ).map { | val | val.to_i }
	break if 0 == h && 0 == w
	
	pa = [ "#", "." ]
	for i in ( 0 ... h ) 
		for j in ( 0 ... w )
			print( "#{pa[(i+j)%2]}" )
		end
		print( "\n" )
	end
	print( "\n" )
end