// ConsoleApplication211.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iomanip>
#include <iostream>
#include <functional>
#include <algorithm>
#include <math.h>
#include <cmath>
#include <string>
#include <cstring>
#include <vector>
#include<set>
#include<map>
#include <time.h>
#include <fstream>
typedef long long ll;
using namespace std;

/*
4
13 7 5
7 13 6
14 3 12
15 6 16
0
*/
int main(){

	map<pair<int, int>,int >mp;
	int n;
	cin >> n;
	int ans = 0;
	int x[2001], y[2001];
	for (int i = 0; i < n; i++){

		cin >>x[i]>> y[i];

	}
	map<pair<int, int>, int >mp2;
	for (int i = 0; i < n; i++){
		for (int k = i+1; k < n; k++){

				pair<int, int> d,d2,d3,d4;
				d.first =  -(x[k] - x[i]);
				d.second =  (y[i] - y[k]);
				d2.first = -d.first;
				d2.second = -d.second;

				ans +=  mp[d];
				ans +=   mp2[d2];
				//ans += mp[d2];
				/*if (d.first==-1&&d.second==0){
					cout << d.first << d.second << '\n';
					cout << mp[d]<<'\t'<<ans << "\n";
				}*/

				++mp2[d2];
				++mp[d];


		}
	}
	cout << ans;
}