### COCI 2006/2007, Contest #2

## Task SJECIĆ TA

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

## Input3 ## Output0 |
## Input4 ## Output1 |
## Input6 ## Output15 |

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

## Comments (Search)

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