#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
bool ok[2001][2001];
int main() {
  {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
  }
  int n;
  cin >> n;
  memset(ok, false, sizeof(ok));
  pair<int, int> a[n];
  for (int i = 0; i <= n - 1; i++) {
    cin >> a[i].first >> a[i].second;
    ok[a[i].first + 1000][a[i].second + 1000] = true;
  }
  int res = 0;
  for (int i = 0; i <= n - 1; i++) {
    for (int j = i + 1; j <= n - 1; j++) {
      int x = a[i].first + a[j].first;
      int y = a[i].second + a[j].second;
      if (x & 1 || y & 1) continue;
      if (ok[x / 2 + 1000][y / 2 + 1000]) res++;
    }
  }
  cout << res;
  return 0;
}
