A

A题没什么好说的，大力膜你一下就好

Bob的移动策略有三种：

A题

坑点

1. 开unsigned long long

2. 这样写是不符合基本法的，会溢出掉的

题目描述

Vladik often travels by trains. He remembered some of his trips especially well and I would like to tell you about one of these trips:

Vladik is at initial train station, and now n people (including Vladik) want to get on the train. They are already lined up in some order, and for each of them the city code $a_i$ is known (the code of the city in which they are going to).