시간 제한메모리 제한제출정답맞힌 사람정답 비율
1 초 64 MB75524445373360.035%

문제

KSG 편의점에서는 과일우유, 드링킹요구르트 등의 유제품을 '2+1 세일'하는 행사를 하고 있습니다. KSG 편의점에서 유제품 3개를 한 번에 산다면 그중에서 가장 싼 것은 무료로 지불하고 나머지 두 개의 제품 가격만 지불하면 됩니다. 한 번에 3개의 유제품을 사지 않는다면 할인 없이 정가를 지불해야 합니다.

예를 들어, 7개의 유제품이 있어서 각 제품의 가격이 10, 9, 4, 2, 6, 4, 3이고 재현이가 (10, 3, 2), (4, 6, 4), (9)로 총 3번에 걸쳐서 물건을 산다면 첫 번째 꾸러미에서는 13원을, 두 번째 꾸러미에서는 10원을, 세 번째 꾸러미에서는 9원을 지불해야 합니다.

재현이는 KSG 편의점에서 친구들과 같이 먹을 총 N팩의 유제품을 구입하려고 합니다. 재현이를 도와 최소비용으로 유제품을 구입할 수 있도록 도와주세요!

입력

첫 번째 줄에는 유제품의 수 N (1 ≤ N ≤ 100,000)이 주어집니다.

두 번째 줄부터 N개의 줄에는 각 유제품의 가격 Ci (1 ≤ Ci ≤ 100,000)가 주어집니다.

출력

재현이가 N개의 유제품을 모두 살 때 필요한 최소비용을 출력합니다. 정답은 231-1보다 작거나 같다.

예제 입력 1

4
3
2
3
2

예제 출력 1

8

예제 입력 2

6
6
4
5
5
5
5

예제 출력 2

21

힌트

예제 1 : 재현이가 (3, 2, 2), (3)으로 총 2번에 걸쳐서 유제품을 사면 됩니다.

예제 2 : 재현이가 (6, 4, 5), (5, 5, 5)로 총 2번에 걸쳐서 유제품을 사면 됩니다.

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

출처

Contest > Croatian Open Competition in Informatics > COCI 2015/2016 > Contest #1 2번