There are $n$ points on the plane, ($x_1, y_1$),($x_2,y_2$)…($x_n,y_n$), $x_i< x_{i+1}$,$0< y_i$

You need to place several rectangles to cover all of them with the following constraints.

(a point is covered if it lies inside the rectangle or on the side of the rectangle)

1. The bottom side of the rectangle should be $x$-axis
2. The cost of a rectangle is $height\times(width + k)$ ($k$ is given by input)
3. Any two different rectangles can't have an intersection
4. the rectangle can degenerate to two lines, which means $width = 0$

Please calculate the minimum cost to cover all of the points.

Input

The first line contains two integers,

$n$ and $k$ ($1 \le n \le4\times10^5, 1\le k \le 10^6$) ---

the number of points and the coefficient described in the problem.

Each of the next $m$ lines contains two integers,

$x_i$ and $y_i$($-10^6 \le x_i \le 10^6, 1\le y_i \le 10^6$)--- meaning $i^{th}$ point is at ($x_i$ , $y_i$).

Output

Output the minimum cost to cover all of the points.

Sample Input 1

1 2
-666 666

Sample Output 1

1332

Sample Input 2

2 66666
-666 666
666 666

Sample Output 2

45286668