The Chess Board

You are given a square grid consisting of $n\times n$ black and white small squares. This grid can also be represented as a chess board of $\frac{n}{k}$ rows and $\frac{n}{k}$ columns, where each cell consists of $k\times k$ small squares of one color. You need to calculate the number of white squares in this grid.

Example of the board for $n=6$ and $k=3$. As you can see, there are $18$ white squares on it. The lighter color is white and the other is black.

Please note that the cell in the first row and the first column is white.

Input

The first line contains two integers $n$ and $k$ $(1\le n,k\le 100)$ — the size of a grid and each cell respectively. It is guaranteed that $n$ is divisible by $k$.

Output

You have to output a single line containing one integer: the number of white squares on a grid.

Examples

Scoring

1. ($5$ points): $n=1$;

2. ($10$ points): $k=1$;

3. ($15$ points): $\frac{n}{k}$ is even;

4. ($20$ points): no additional constraints.