Problem:
Score : 300 points

Problem Statement

There are 3N participants in AtCoder Group Contest.
The strength of the i-th participant is represented by an integer a_i.
They will form N teams, each consisting of three participants.
No participant may belong to multiple teams.

The strength of a team is defined as the second largest strength among its members.
For example, a team of participants of strength 1, 5, 2 has a strength 2, and a team of three participants of strength 3, 2, 3 has a strength 3.

Find the maximum possible sum of the strengths of N teams.

Constraints

1 ≤ N ≤ 10^5

1 ≤ a_i ≤ 10^{9}

a_i are integers.

Input

Input is given from Standard Input in the following format:

N
a_1 a_2 ... a_{3N}

Output

Print the answer.

Sample Input 1

2
5 2 8 5 1 5

Sample Output 1

10

The following is one formation of teams that maximizes the sum of the strengths of teams:

Team 1: consists of the first, fourth and fifth participants.

Team 2: consists of the second, third and sixth participants.

Sample Input 2

10
1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000

Sample Output 2

10000000000

The sum of the strengths can be quite large.

Solution in Kotlin (1.0.0) (judge verdict: Wrong Answer)

fun main(args: Array<String>) {

    val teamNum = readLine()!!.toInt()
    val numbers = readLine()!!.split(" ").map { it.toInt() }

    val sortedNumbers = numbers.sortedDescending()

    // LOOK 演算結果が10桁超えがあれば、longにする必要がある。2147483647 = 2の31乗-1
    var result = 0L

    // 0..2だと0, 1, 2で3順するので2回ループしたいのであれば、0 until teamNumだし、1始まりなら、1..teamNumで2回ループ
    // 今回のケースでいえば、sortedNumbersをループして、index0を飛ばして、teamNum回ループする
    for ((index, value) in sortedNumbers.withIndex()) {

        if (index == 0)
        // 初回オブジェクトには何もしない
        else if (index == teamNum) {
            result += value
            break
        } else {
            result += value
        }
    }
    println(result)
}