Have you ever experienced that when you open the door of your dormitory again, you find all the beds are empty and there's nothing on the bed board. They're gone. You think it's just a summer vacation and they will be back soon. But actually, it's not the case. They're gone and they go to pursue their future. Those who accompany you for four years, those whom you once bothered about and even scolded secretly behind their backs, leave you a ground full of sadness after they're gone.