Flower Dance

题号：NC51629
时间限制：C/C++/Rust/Pascal 1秒，其他语言2秒
空间限制：C/C++/Rust/Pascal 512 M，其他语言1024 M
64bit IO Format: %lld

题目描述

Gromah and LZR have entered the sixth level.

There are $n_{}$ pairwise distinct points on the wall, each can be described as $P_i(x_i, y_i) \;(1\le i\le n)$ in a 2-dimensional rectangular coordinate system.

LZR finds a note board saying that four distinct points $A,B,C,D{}$ form a flower if there exists a point among the four points strictly inside the triangle formed by the other three points, where the triangle should be non-degenerate.

So the password of this level is naturally the number of tuples $(i,j,k,l)(1 \le i < j < k < l \le n)$ that $P_i, P_j, P_k, P_l$ form a flower.

Please help them to calculate the answer.

输入描述:

The first line contains one positive integer , denoting the number of points.

Following  lines each contains two integers , denoting a point.



 points are pairwise distinct.

输出描述:

Print a non-negative integer in a single line, denoting the number of flowers.

示例1

输入

复制

输出

复制

说明

The 5 flowers are
,
,
,
,
.