#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }
#define COLOR(s) ("\x1b[" s "m")


int N;
vector<Int> X, Y;

int main() {
  for (; ~scanf("%d", &N); ) {
    X.resize(N);
    Y.resize(N);
    for (int u = 0; u < N; ++u) {
      scanf("%lld%lld", &X[u], &Y[u]);
      X[u] *= 2;
      Y[u] *= 2;
    }
    
    vector<pair<pair<Int, Int>, pair<Int, Int>>> es;
    for (int u = 0; u < N; ++u) for (int v = u + 1; v < N; ++v) {
      const Int ox = (X[u] + X[v]) / 2;
      const Int oy = (Y[u] + Y[v]) / 2;
      Int dx = X[u] - ox;
      Int dy = Y[u] - oy;
      const Int g = __gcd(dx, dy);
      dx /= g;
      dy /= g;
      if (dy < 0 || (dy == 0 && dx < 0)) {
        dx = -dx;
        dy = -dy;
      }
      es.emplace_back(make_pair(ox, oy), make_pair(dx, dy));
    }
    sort(es.begin(), es.end());
    const int esLen = es.size();
    Int ans = 0;
    for (int i = 0, j = 0; i < esLen; i = j) {
      for (; j < esLen && es[i].first == es[j].first; ++j) {}
      for (int k = i; k < j; ++k) {
        const Int dx = es[k].second.first;
        const Int dy = es[k].second.second;
        auto res = equal_range(es.begin() + i, es.begin() + j, make_pair(es[i].first, make_pair(-dy, dx)));
        ans += (res.second - res.first);
      }
    }
    printf("%lld\n", ans);
  }
  return 0;
}