8096번 - Monochromatic Triangles 다국어

문제

There are n points given in a space. There are no three points, such that they lie on the same straight line. Each pair of points is connected by a segment coloured red or black. Each triangle, whose sides have the same colour is called a monochromatic triangle. We are given a list of all red segments and we want to find the number of all monochromatic triangles.

Write a program that:

• reads from the standard input the following data: the number of points, the number of red segments and their list,
• finds the number of monochromatic triangles,
• writes the result to the standard output.

입력

In the first line of the standard input there is one integer n, 3 ≤ n ≤ 1,000, which equals the number of points. In the second line there is one integer m, 0 ≤ m ≤ 250,000, which equals the number of red segments.

In each of the following m lines there are two integers p and k separated by a single space, 1 ≤ p < k ≤ n. They are numbers of vertices which are ends of a red segment.

출력

In the first line of the standard output there should be written one integer — the number of monochromatic triangles.

제한

힌트