Get Max Throughput

Split some of the servers into non-overlapping triples; each triple contributes the median of its three throughputs, and leftover servers may go unused. Find the maximum total contribution.

输入格式

The first line contains n (1..100000), and the second line contains n throughputs (1..10⁹).

输出格式

Output a single integer, the answer required by the problem.

样例 1

输入：

5
2 3 4 5 4

输出：

4

样例 2

输入：

2
1 2

输出：

0

样例 3

输入：

6
1 2 3 4 5 6

输出：

8

样例说明

Example 1: five servers can form at most one group; choosing throughputs 3, 4 and 5 gives median 4. Example 2: there are fewer than three servers, so no group can be formed and the answer is 0. Example 3: the servers can be split into [1,5,6] and [2,3,4], with medians 5 and 3, total 8.