Statement

Timothy has an integer $x$. He creates a sequence of length $n$ by alternating between the integer $x$ and $-x$, starting with $x$.

For example, if $n = 5$, the sequence is as follows: $x, -x, x, -x, x$.

He asks you to find the sum of all integers in the sequence.

Input

The input consists of a single line containing two integers $x$ and $n$ separated by a space, where $x$ satisfies $-1\times 10^{18}\leqslant x\leqslant 1\times 10^{18}$ and $n$ satisfies $0\leqslant n\leqslant 1\times 10^{18}$

Output

Output the sum of all integers in this sequence.

Samples

6 3

6

114514 1919810

0

1145141919810 123

1145141919810