Boredom

### 题目描述 亚力克斯不喜欢无聊。 所以每当他感到无聊他就会想出一些游戏。一个冬天的晚上他想出了一个游戏并且决定开始玩这个游戏。 给定一个有 $n$ 个元素的序列 $\{a_n\}$。你可以做若干次操作。在一次操作中我们可以取出一个数（假设他为 $x$）并删除它，同时删除所有的序列中值为 $x+1$ 和 $x-1$ 的数。这一步操作会给玩家加上 $x$ 分。 ### 输入输出格式 输入格式：第一行一个整数 $n(1\le n\le 10^5)$,说明这个序列有多少数。 第二行 $n$ 个整数，分别表示 $a_1,a_2,\cdots,a_n$。 输出格式：一个整数，表示玩家最多能获得多少分。 说明： 对于样例 3，第一步我们取 $2$，序列变为 $[2,2,2,2]$。接下来每一步都取 $2$，最后获得 $10$ 分。

Alex doesn't like boredom. That's why whenever he gets bored, he comes up with games. One long winter evening he came up with a game and decided to play it. Given a sequence $ a $ consisting of $ n $ integers. The player can make several steps. In a single step he can choose an element of the sequence (let's denote it $ a_{k} $ ) and delete it, at that all elements equal to $ a_{k}+1 $ and $ a_{k}-1 $ also must be deleted from the sequence. That step brings $ a_{k} $ points to the player. Alex is a perfectionist, so he decided to get as many points as possible. Help him.

The first line contains integer $ n $ ( $ 1<=n<=10^{5} $ ) that shows how many numbers are in Alex's sequence. The second line contains $ n $ integers $ a_{1} $ , $ a_{2} $ , ..., $ a_{n} $ ( $ 1<=a_{i}<=10^{5} $ ).

Print a single integer — the maximum number of points that Alex can earn.

2
1 2

2

3
1 2 3

4

9
1 2 1 3 2 2 2 2 3

10

Consider the third test example. At first step we need to choose any element equal to $ 2 $ . After that step our sequence looks like this $ [2,2,2,2] $ . Then we do $ 4 $ steps, on each step we choose any element equals to $ 2 $ . In total we earn $ 10 $ points.