Delivery Forces

Gry finally becomes the Executive Courier Officer in "Universe Express". He has  subordinate couriers with some delivery strength . The delivery strength of a team of three people is the median of their strength, i.e., the middle element after the sorting. Please help Gry to split the couriers into  teams of three people in order to maximize the total delivery strength of "Universe Express". The total strength is the sum of the strength of these  teams.

Input

itemize
One line containing the number of couriers in the company,  (), where  is a multiple of .
One line containing the strengths of the  couriers  ().
itemize

Output
The sole line of the output should contain the maximal strength of "Universe Express".