Roma and Changing Signs

2000ms

262144K

Description:

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.

Input:

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.

Output:

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

Sample Input:

3 2
-1 -1 1

Sample Output:

Sample Input:

3 1
-1 -1 1

Sample Output:

Note:

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.

Informação

Provedor Codeforces

Código CF262B