Xiao Wang and Xiao Li are to process the same number of the same type of parts, and they start working at the same time. It is known that Xiao Wang processes 15 per hour, and must rest for 1 hour after every 2 hours of work; Xiao Li works without interruption, processing 12 per hour. As a result, they both finish at the same moment. Xiao Wang processes $\qquad$ parts.