#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <fstream>
using namespace std;

const string file = "trapez";

const string infile = file + ".in";
const string outfile = file + ".out";

const int INF = 0x3f3f3f3f;


struct Point2D
{
	int x;
	int y;
};


bool pred(const Point2D& p1, const Point2D& p2)
{
	return p1.y * p2.x < p1.x * p2.y;
}


int predComp(const Point2D& p1, const Point2D& p2)
{
	return p1.y * p2.x == p1.x * p2.y;
}

int N;
int pX;
int pY;
vector<Point2D> pante;
vector<Point2D> points;
int Sol;
int main()
{
	fstream fin(infile.c_str(), ios::in);
	fin >> N;
	points.resize(N);
	pante.reserve(N * N);
	for(int i = 0; i < N; i++)
	{
		fin >> points[i].x;
		fin >> points[i].y;
	}
	fin.close();

	for(int i = 0; i < N; i++)
	{
		for(int j = i + 1; j < N; j++)
		{
			Point2D p;
			p.x = points[i].x - points[j].x;
			p.y = points[i].y - points[j].y;


			if(p.x == 0)
			{
				pX++;
				continue;
			}
			if(p.y == 0)
			{
				pY++;
				continue;
			}

			pante.push_back(p);
		}
	}

	sort(pante.begin(), pante.end(), pred);
	

	int cont = 1;
	Point2D prev = pante.front();
	for(vector<Point2D>::iterator itr = pante.begin() + 1;
		itr != pante.end();
		itr++)
	{
		if(predComp(prev, *itr))
		{
			cont++;
		}
		else
		{
			if(cont >= 2)
			{
				Sol += cont * (cont - 1)/2;
			}
			cont = 1;
			prev = *itr;
		}
	}

	if(cont >= 2)
	{
		Sol += cont * (cont-1)/2;
	}

	if(pX >= 2)
		Sol += pX * (pX - 1) / 2;
	if(pY >= 2)
		Sol += pY * (pY - 1) / 2;

	fstream fout(outfile.c_str(), ios::out);
	fout << Sol << "\n";
	fout.close();
}