PROGRAMMING:Area of symmetrical figure

There are some scattered points in the two-dimensional plane coordinate system. Firstly, the scattered points need to be sorted according to the Y coordinate value of the points, and then the points are connected into an open polygonal curve. Given an axis of rotation parallel to the y-axis, x = X$$_{ 0} $$, the polygon curve is rotated according to the rotation axis X = X$$_{ 0} $$, and connect two line segments between the original point and the mirror point at the bottom and the top to form a closed symmetrical figure. Please calculate the area of the figure. X of the axis of symmetry$$_{ 0} $$coordinates are either greater than the X coordinates of all scattered points or less than the X coordinates of all points, so there is no self intersection in the symmetric graph. The topic ensures that the Y coordinate values of all scattered points are different.
###Input format:
The first line gives the X coordinate X of the axis of rotation parallel to the Y axis$$_{ 0} $$, the second line gives the positive integer n (2 ≤ n ≤ 10 $$^ 4 $$), which represents the number of scattered points, and the next N lines give the X and Y coordinates of scattered points.
###Output format:
Output the area of the symmetrical figure, keeping 2 decimal places.
###Input example:
For example, enter 1:
```in
three
two
-1.5 1.5
1.5 -1.5
```
Output:
```out
eighteen
```
For example, enter 2:
```in
-10.25
five
-1.5 1.5
-1.5 4.5
1.5 -1.5
10.5 -11.5
21.52 20.5
```
Output:
```out
one thousand and eighty-seven point three two
```






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