From atop a satellite, Nick has drawn
Constraints
All lines are pairwise distinct.
No three lines intersect at a common point.
Input Specification
The first line contains a single positive integer,
The next
Output Specification
Output the number of such triangles.
Sample Input
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4
0 0 0 10
0 0 10 0
0 5 5 5
0 10 10 0
Sample Output
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1
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