給你一個數列, 找出數列上數字相加時最好的成本是多少

The problem name reflects your task; just add a set of numbers. But you may feel yourselves condescended, to write a program just to add a set of numbers. Such a problem will simply question your erudition. So, let us add some flavor of ingenuity to it.

Addition operation requires cost now, and the cost is the summation of those two tobe added. So, to add 1 and 10, you need a cost of 11. If you want to add 1, 2 and 3.

There are three ways: 

(1) 1 + 2 = 3, cost = 3; 3 + 3 = 6, cost = 6; Total = 9
(2) 1 + 3 = 4, cost = 4; 4 + 2 = 6, cost = 6; Total = 10
(3) 2 + 3 = 5, cost = 5; 5 + 1 = 6, cost = 6; Total = 11

Your task is write a program to add a set of integers so that the cost is minimized.