Cardboard Mountains

Limits 1s, 512 MB

Alice has been given the responsibility of creating the background of the annual play in her school. The background consists of Mountains. One such Background-

Figure 1: A Cardboard Mountain Background.

The Mountains' characteristics are —

  1. Mountains are triangles whose base is on the floor.

  2. A stick is placed vertically from the floor to the peak of the mountain to support it.

  3. The lower right vertex of a mountain starts from the stick of the mountain to the immediate left and the lower right vertex on the stick of the mountain to the immediate right.

  4. The left-most mountain's lower left vertex is on the lower left corner of the background.

  5. The right-most mountain's lower right vertex is on the lower right corner of the background.

  6. The width of the stick is negligible.

Note that, a mountain m1m_1 is defined left (or, right) to another mountain m2m_2 if the stick supporting m1m_1 is strictly on the left (or, right respectively) of m2m_2. Furthermore, m1m_1 is the immediate left (or, right) of m2m_2 if among all of the mountains who are on left (or, right) of m2m_2, m1m_1 is the right-most (or, left-most respectively).

The Mountains are traditionally created this way. But Alice being a problem solver has thought of an easier way to create the mountains. Alice thought of doing the following —

  1. Consider the background as a 2D Cartesian plane, where the lower left corner will be the origin and the lower right corner will be (X,0)(X, 0), where XX is the length of the background.

  2. Fix the coordinates of the peaks of NN Mountains on the Cartesian plane, then draw the Mountains respecting their characteristics, on a paper for reference.

  3. Cut a single cardboard shape according to that reference.

Let’s say Alice has generated 5 mountain peaks’ co-ordinates. They are (8,6)(8, 6), (22,8)(22, 8), (4,10)(4, 10), (13,12)(13, 12) and (18,14)(18, 14). The length of the background is 2525 units. The final shape of the cardboard shape can be denoted by figure 1.

Alice is wondering what would be the area of the final cardboard shape for the Mountains on the background after cutting. Given the coordinates of the NN mountain tips, and the length of the background, XX, can you calculate the area of the final cardboard shape?


The first line contains a single integer TT (1T104)(1≤T≤10^4), the number of test cases.

The first line of each test case contains two space-separated integers, NN(1N2×105)(1 \le N \le 2 \times 10^5) and XX(2X106)(2 \le X \le 10^6), denoting the number of peaks and the background’s length respectively.

The ithi^{th} line of the next NNlines contain two integers xix_i and yiy_i (0<xi<X,  1yi106)(0 < x_i < X, \; 1 \le y_i \le 10^6), the coordinate of the ithi^{th} mountain.

The sum of NN all over test cases doesn’t exceed 2×1052 \times 10^5.


For each test case, output the area of the final cardboard shape. Your answer will be considered correct if the relative or absolute difference is less than 10610^{-6}. That means, if your answer is AA and jury’s answer is BB, your answer will be considered correct if ABmax(1,B)<106\frac{|A-B|}{max(1,B)}<10^{-6}.


5 25
8 6
18 14
4 10
13 12
22 8