12个数字两两组合一共多少种情况

简介：The final exam only lasted two days. On the last day, when Su Can was waiting for Cheng Keshu outside the examination room, the second snow of winter began to fall in Pinghai small town. White snow fell from the heavy leaden sky. Cheng Keshu walked out of the classroom. When I came out, I saw Su Can standing in the snow.