help in geometry problem

Правка en1, от It_Wasnt_Me, 2019-10-31 22:14:19

[contest:https://codeforces.net/contest/552/problem/D] in this problem, shortly you should count all number of triangles with non-zero area.

My idea was to count all triangle I could which is NC3 then I will subtract zero-area triangles

zero-area triangle will occur if there is 3 points on the same line(horizontal, vertical) or have same diagonal.

Unfortunately I received (Wrong answer) and I can't prove why my solution is wrong, I tested it on several testcases and it gives Right answer.

https://codeforces.net/contest/552/submission/63943093 Any help

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  Rev. Язык Кто Когда Δ Комментарий
en3 Английский It_Wasnt_Me 2019-10-31 22:19:35 41
en2 Английский It_Wasnt_Me 2019-10-31 22:15:09 48
en1 Английский It_Wasnt_Me 2019-10-31 22:14:19 599 Initial revision (published)