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.

The first line contains two integers $ n $ and $ k $ $ (1

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

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 $ .