D. Tokitsukaze and Strange Rectangletime limit per test3 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard outputThere are n points on the plane, the i-th of which is at (x_i, y_i). Tokitsukaze wants to draw a strange rectangular area and pick all the points in the area.The strange area is enclosed by three lines, x = l, y = a and x = r, as its left side, its bottom side and its right side respectively, where l, r and a can be any real numbers satisfying that l < r. The upper side of the area is boundless, which you can regard as a line parallel to the x-axis at infinity. The following figure shows a strange rectangular area.  A point (x_i, y_i) is in the strange rectangular area if and only if l < x_i < r and y_i > a. For example, in the above figure, p_1 is in the area while p_2 is not.Tokitsukaze wants to know how many different non-empty sets she can obtain by picking all the points in a strange rectangular area, where we think two sets are different if there exists at least one point in one set of them but not in the other.InputThe first line contains a single integer n (1 \leq n \leq 2 \times 10^5) — the number of points on the plane.The i-th of the next n lines contains two integers x_i, y_i (1 \leq x_i, y_i \leq 10^9) — the coordinates of the i-th point.All points are distinct.OutputPrint a single integer — the number of different non-empty sets of points she can obtain.ExamplesInput31 11 21 3Output3Input31 12 13 1Output6Input42 12 23 13 2Output6NoteFor the first example, there is exactly one set having k points for k = 1, 2, 3, so the total number is 3.For the second example, the numbers of sets having k points for k = 1, 2, 3 are 3, 2, 1 respectively, and their sum is 6.For the third example, as the following figure shows, there are  2 sets having one point;  3 sets having two points;  1 set having four points. Therefore, the number of different non-empty sets in this example is 2 + 3 + 0 + 1 = 6.  
Input31 11 21 3
Output3
['data structures', 'divide and conquer', 'sortings', 'two pointers', '*2000']