CF262B.Roma and Changing Signs

Roma works in a company that sells TVs. Now he has to prepare a report for the last year.

Roma has got a list of the company's incomes. The list is a sequence that consists of n integers. The total income of the company is the sum of all integers in sequence. Roma decided to perform exactly k changes of signs of several numbers in the sequence. He can also change the sign of a number one, two or more times.

The operation of changing a number's sign is the operation of multiplying this number by -1.

Help Roma perform the changes so as to make the total income of the company (the sum of numbers in the resulting sequence) maximum. Note that Roma should perform exactly k changes.

罗玛在一家销售电视机的公司工作。现在他需要为上一年度准备一份报告。

罗玛获得了一份公司收入清单。该清单是一个由 $n$ 个整数组成的序列。公司的总收入等于该序列中所有整数的和。罗玛决定恰好执行 $k$ 次对序列中若干数字的符号更改操作。他可以对同一个数字更改符号一次、两次或更多次。

将一个数字的符号取反，即对该数字乘以 $-1$。

请帮助罗玛执行这些更改操作，使得公司最终的总收入（即更改后序列中所有数字的和）尽可能大。注意：罗玛必须恰好执行 $k$ 次更改操作。

The first line contains two integers n and k (1 ≤ n, k ≤ 105), showing, how many numbers are in the sequence and how many swaps are to be made.

The second line contains a non-decreasing sequence, consisting of n integers a__i (|a__i| ≤ 104).

The numbers in the lines are separated by single spaces. Please note that the given sequence is sorted in non-decreasing order.

第一行包含两个整数 $n$ 和 $k$（$1 \leq n, k \leq 10^5$），分别表示序列中数字的个数以及需要执行的交换次数。

第二行包含一个非递减序列，由 $n$ 个整数 $a_i$ 组成（$|a_i| \leq 10^4$）。

每行中的数字以单个空格分隔。请注意，给定的序列为非递减排序。

In the single line print the answer to the problem — the maximum total income that we can obtain after exactly k changes.

在单行中输出问题的答案——经过恰好 k 次变换后所能获得的最大总收入。

In the first sample we can get sequence [1, 1, 1], thus the total income equals 3.

In the second test, the optimal strategy is to get sequence [-1, 1, 1], thus the total income equals 1.

在第一个样例中，我们可以得到序列 [1, 1, 1]，因此总收入为 3。

在第二个测试用例中，最优策略是得到序列 [-1, 1, 1]，因此总收入为 1。