#include <bits/stdc++.h>
using namespace std;
pair<double, double> midpoint(double x1, double y1, double x2, double y2) {
  return {(x1 + x2) / 2, (y1 + y2) / 2};
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  map<pair<double, double>, int> mp;
  pair<double, double> pr[n + 5];
  for (int i = 0; i < n; i++) {
    cin >> pr[i].first >> pr[i].second;
    mp[pr[i]]++;
  }
  int ans = 0;
  for (int i = 0; i < n; i++) {
    for (int j = i + 1; j < n; j++) {
      if (mp.find(midpoint(pr[i].first, pr[i].second, pr[j].first,
                           pr[j].second)) != mp.end())
        ans++;
    }
  }
  cout << ans;
  return 0;
}
