CF442C.Artem and Array

Artem has an array of n positive integers. Artem decided to play with it. The game consists of n moves. Each move goes like this. Artem chooses some element of the array and removes it. For that, he gets min(a, b) points, where a and b are numbers that were adjacent with the removed number. If the number doesn't have an adjacent number to the left or right, Artem doesn't get any points.

After the element is removed, the two parts of the array glue together resulting in the new array that Artem continues playing with. Borya wondered what maximum total number of points Artem can get as he plays this game.

阿尔泰姆有一个包含 $n$ 个正整数的数组。阿尔泰姆决定和这个数组玩一个游戏。游戏共进行 $n$ 轮，每轮操作如下：阿尔泰姆选择数组中的某个元素并将其移除；他因此获得 $\min(a,\,b)$ 分，其中 $a$ 和 $b$ 是被移除数字左右两侧相邻的数。若该数左侧或右侧没有相邻元素，则阿尔泰姆不得分。

被移除元素后，数组的左右两部分拼接在一起，形成一个新的数组，阿尔泰姆继续在该新数组上进行后续操作。鲍里亚想知道：阿尔泰姆在整个游戏中最多能获得多少总分？

The first line contains a single integer n (1 ≤ n ≤ 5·105) — the number of elements in the array. The next line contains n integers a__i (1 ≤ a__i ≤ 106) — the values of the array elements.

第一行包含一个整数 $n$（$1 \leq n \leq 5 \cdot 10^5$）—— 数组中元素的个数。
下一行包含 $n$ 个整数 $a_i$（$1 \leq a_i \leq 10^6$）—— 数组元素的值。

In a single line print a single integer — the maximum number of points Artem can get.

在一行中输出一个整数——Artem 能获得的最高分数。