12个数字两两组合一共多少种情况

简介：On July 21, various units of the Ming army arrived around Songshan one after another, including Ningyuan Cavalry Battalion, Ningyuan Battalion, Shanhai Battalion, Jingying Battalion, Qin Battalion, Jizhou Battalion, Changping Battalion, Yutian Battalion, Miyun Battalion, Baoding Fengtai Battalion, and more than ten joint battalions. Here, flags shook the sky and blocked out the sun, and camps were scattered all over the mountains and plains.