#include <iostream>
#include <fstream>
#include <set>
#include <algorithm>
#include <vector>

using namespace std;

ifstream fin("patrate3.in");
ofstream fout("patrate3.out");

set <pair<int, int>> set_puncte;

int main()
{
	int n, nr = 0;
	fin >> n;

	vector <pair<int, int>> puncte(n);

	for (int i = 0; i < n; i++)
	{
		double x, y;
		fin >> x >> y;

		x = round(x * 10000);
		y = round(y * 10000);

		puncte[i].first = x;
		puncte[i].second = y;

		set_puncte.insert(puncte[i]);
	}

	for (int i = 0; i < n-1; i++)
		for (int j = i + 1; j < n; j++)
		{
			int dif1 = puncte[j].first - puncte[i].first;
			int dif2 = puncte[i].second - puncte[j].second;

			pair<int, int> pct1, pct2;
			pct1 = { puncte[i].first + dif2, puncte[i].second + dif1 };
			pct2 = { puncte[j].first + dif2, puncte[j].second + dif1 };

			if (set_puncte.find(pct1) != set_puncte.end() && set_puncte.find(pct2) != set_puncte.end())
				nr++;
		}

	fout << nr / 2;
	return 0;
}