COCI 2006/2007, Contest #2

Task SJECIŠTA

Consider a convex polygon with N vertices, with the additional property that no three diagonals intersect in a single point. Find the number of intersections between pairs of diagonals in such a polygon.

The figure below shows one such polygon with 6 vertices.

Note: a polygon is convex if all of its interior angles are less than 180 degrees.

Input

The first and only line of input contains a single integer N (3 ≤ N ≤ 100).

Output

Output the number of intersections on a single line.

Sample Tests

3

0

4

1

6

15

All Submissions
Best Solutions

Point Value: 7
Time Limit: 1.00s
Memory Limit: 32M
Added: Jul 14, 2013

Languages Allowed:
C++03, PAS, C, HASK, ASM, RUBY, PYTH2, JAVA, PHP, SCM, CAML, PERL, C#, C++11, PYTH3

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