考虑一个拥有 $N$ 个顶点的凸多边形，它满足一个额外的性质：任意三条对角线都不交于同一点。求该多边形中对角线两两相交的交点个数。
下图展示了一个拥有 6 个顶点的此类多边形。
注意：如果一个多边形的所有内角都小于 180 度，则称其为凸多边形。
输入格式
输入只有一行，包含一个整数 $N$（$3 \le N \le 100$）。
输出格式
输出一行一个整数，表示交点的个数。
样例
输入 1
3
输出 1
0
输入 2
4
输出 2
1
输入 3
6
输出 3
15
QOJ.ac
QOJ
Time Limit: 1.0 s
Memory Limit: 32 MB
Total points: 40
#17554. 交点
Statistics
The problem was used in the following contests:
AI Translation —
This statement was translated using AI and may contain inaccuracies. Please refer to the original statement if in doubt.
Discussions
About Discussions
The discussion section is only for posting: General Discussions (problem-solving strategies, alternative approaches), and Off-topic conversations.
This is NOT for reporting issues! If you want to report bugs or errors, please use the Issues section below.
Open Discussions 0
No discussions in this category.
Issues
About Issues
If you find any issues with the problem (statement, scoring, time/memory limits, test cases, etc.), you may submit an issue here. A problem moderator will review your issue.
Guidelines:
- This is not a place to publish discussions, editorials, or requests to debug your code. Issues are only visible to you and problem moderators.
- Do not submit duplicated issues.
- Issues must be filed in English or Chinese only.
Active Issues 0
No issues in this category.
Closed/Resolved Issues 0
No issues in this category.