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Counting triangles
You may have seen puzzles for children in which one is required to count the number of distinct triangles in a given figure. In this problem you have to write a program to do precisely that: write a a program that accepts a set of n lines segments in a plane as input and gives the number of distinct triangles formed by these lines segments as outputs.
INPUT
The first line contain a positive integer n,which specifies number of line segments.
Next n line contain (x1,y1) and (x2,y2) are the coordinates of the start and end point respectively. Assume that n<=20 and -20<= x1,y1,x2,y2 <=20.Also assume that no two line fully or partially overlap.
Output
Number of distinct triangles that can be formed from the given line segments.
Sample Input
6
3 1 5 1
3 1 3 2
3 2 4 2
4 2 5 1
3 2 5 1
3 1 4 2
Sample Output
8