先贴几个链接，以后再写
欧几里得算法讲解
模板题：https://vjudge.net/contest/389069#problem/D
题解：https://blog.csdn.net/sr_19930829/article/details/38057609?utm_medium=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-1.channel_param&depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-1.channel_param