U461745 洛谷枢纽站

题目背景

以下为洛谷主要网页入口 [灌水区](https://www.luogu.com.cn/discuss?forum=relevantaffairs) [首页](https://www.luogu.com.cn/) [题库](https://www.luogu.com.cn/problem/list) [洛谷官方团队](https://www.luogu.com.cn/team/1000) [洛谷管理员名单](https://www.luogu.com.cn/discuss/327478)

题目描述

以下为各类比赛样题 [GESP一级样题测试](https://ti.luogu.com.cn/problemset/1101/training) [GESP二级样题测试](https://ti.luogu.com.cn/problemset/1102/training) [GESP三级样题测试](https://ti.luogu.com.cn/problemset/1103/training) [GESP四级样题测试](https://ti.luogu.com.cn/problemset/1104/training) [GESP五级样题测试](https://ti.luogu.com.cn/problemset/1105/training) [GESP六级样题测试](https://ti.luogu.com.cn/problemset/1106/training) [GESP七级样题测试](https://ti.luogu.com.cn/problemset/1107/training) [GESP八级样题测试](https://ti.luogu.com.cn/problemset/1108/training) [其他样题入口](https://ti.luogu.com.cn/problemset/)

输入格式

以下为洛谷官方公告 [洛谷帮助中心](https://help.luogu.com.cn/) [洛谷新用户必读](https://www.luogu.com.cn/discuss/241461) [洛谷主题库题目规范](https://help.luogu.com.cn/rules/academic/problem-standard) [洛谷主题库题解规范](https://help.luogu.com.cn/rules/academic/solution-standard) [洛谷讨论区规范](https://help.luogu.com.cn/rules/community/discuss) [主站操作指南](https://help.luogu.com.cn/manual/luogu/) [洛谷KaTex公式大全](https://www.luogu.com.cn/article/4a81e2tt)

输出格式

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