#include <bits/stdc++.h>
#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("sse,avx,fma,avx2,bmi,bmi2,lzcnt,popcnt")

using namespace std;

void solve() {
  int n;
  cin >> n;

  vector<pair<int, int>> v(n);
  for (auto &p : v)
    cin >> p.first >> p.second;

  map<long long, int> m;
  for (int i = 0; i < n; ++i) {
    for (int j = i + 1; j < n; ++j) {
      int dx = (v[i].first - v[j].first), dy = (v[i].second - v[j].second);

      int d = gcd(abs(dx), abs(dy));
      dx /= d, dy /= d;
      if (dx < 0 || (dx == 0 && dy < 0))
        dx = -dx, dy = -dy;

      auto p = make_pair(dx, dy);
      ++m[*(long long *)&p];
    }
  }

  long long ans = 0;
  for (auto [_, v] : m)
    ans += v * 1LL * (v - 1) / 2;

  cout << ans << endl;
}

int main() {
  freopen("trapez.in", "r", stdin);
  freopen("trapez.out", "w", stdout);
  int t = 1;
  // cin >> t;
  while (t--)
    solve();

  return 0;
}