#include <bits/stdc++.h>
using namespace std;
long long int gcd(long long int a, long long int b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long int lcm(long long int a, long long int b) {
  return a * b / gcd(a, b);
}
long long int fexp(long long int a, long long int b) {
  long long int ans = 1;
  while (b) {
    if (b & 1) ans = ans * a % 1000000007;
    b /= 2;
    a = a * a % 1000000007;
  }
  return ans;
}
long long int inverse(long long int a, long long int p) {
  return fexp(a, p - 2);
}
void ingraph(vector<vector<long long int>>& graph, long long int m) {
  long long int x, y;
  for (long long int i = 0; i < m; i++) {
    cin >> x >> y;
    x--, y--;
    graph[x].push_back(y);
    graph[y].push_back(x);
  }
}
long long int dist(pair<long long int, long long int> a,
                   pair<long long int, long long int> b) {
  return (a.first - b.first) * (a.first - b.first) +
         (a.second - b.second) * (a.second - b.second);
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int t;
  t = 1;
  while (t--) {
    long long int n;
    cin >> n;
    vector<pair<long long int, long long int>> points(n);
    for (long long int i = 0; i < n; i++)
      cin >> points[i].first >> points[i].second;
    map<pair<long double, long long int>, map<long double, long long int>> seg;
    map<long long int, map<long double, long long int>> inf;
    for (long long int i = 0; i < n; i++) {
      for (long long int j = i + 1; j < n; j++) {
        long long int dx = points[i].first - points[j].first;
        long long int dy = points[i].second - points[j].second;
        long long int d = dist(points[i], points[j]);
        if (dx == 0) {
          seg[make_pair((long long int)1e18, d)][points[i].first]++;
        } else {
          long double slope = 1.0 * dy / dx;
          long double intercept = points[i].second - slope * points[i].first;
          seg[make_pair(slope, d)][intercept]++;
        }
      }
    }
    long long int ans = 0;
    map<pair<long double, long long int>,
        map<long double, long long int>>::iterator itr = seg.begin();
    while (itr != seg.end()) {
      long long int sum = 0;
      map<long double, long long int>::iterator fin = itr->second.begin();
      while (fin != itr->second.end()) {
        ans += sum * fin->second;
        sum += fin->second;
        fin++;
      }
      itr++;
    }
    cout << ans / 2;
  }
}
