Boredom
题目描述
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 ak) and delete it, at that all elements equal to ak+1 and ak-1 also must be deleted from the sequence. That step brings ak 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≤105) that shows how many numbers are in Alex's sequence.
The second line contains n integers a1, a2, ..., an (1≤ai≤105).
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.
题目来源：fps-www.educg.net-codeforce-1-2833.xml.zip；FPS 共享题包，题包内第 1530 题。保留原作者与原赛事署名。