#pragma GCC optimize "O3,omit-frame-pointer,inline"
#pragma GCC push_options
#pragma GCC optimize ("unroll-loops")
#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;



signed main () {
  std::ios::sync_with_stdio(false); std::cin.tie(0);
  int n;
  cin >> n;
  vector<int> x(n), y(n);
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
  }


  auto getFraction = [] (int num, int den) {
    int g = __gcd(num, den);
    num /= g;
    den /= g;
    if (den < 0) {
      num *= -1;
      den *= -1;
    }
    if (num == 0) den = 1;
    if (den == 0) num = 1;
    return make_pair(num, den);
  };

  map<tuple<int, int, int, int>, int> mp;
  for (int i = 0; i < n; i++) {
    for (int j = i + 1; j < n; j++) {
      auto [num, den] = getFraction(x[j] - x[i], y[j] - y[i]);
      int centerX = x[i] + x[j];
      int centerY = y[i] + y[j];
      mp[{num, den, centerX, centerY}]++;
    }
  }
  long long ans = 0;
  for (int i = 0; i < n; i++) {
    for (int j = i + 1; j < n; j++) {
      auto [num, den] = getFraction(-(y[i] - y[j]), x[i] - x[j]);
      int centerX = x[i] + x[j];
      int centerY = y[i] + y[j];
      ans += mp[{num, den, centerX, centerY}];
    }
  }
  cout << ans / 2 << endl;
  return 0;  
}