/* -*- coding: utf-8 -*-
 *
 * 2769.cc:  No.2769 Number of Rhombi - yukicoder
 */

#include<cstdio>
#include<map>
#include<algorithm>
#include<tuple>
 
using namespace std;

/* constant */

const int MAX_N = 1000;
const int MAX_M = MAX_N * (MAX_N - 1) / 2;

/* typedef */

using ll = long long;
using tp4 = tuple<int,int,int,int>;
using mtp4i = map<tp4,int>;

/* global variables */

int xs[MAX_N], ys[MAX_N];
tp4 es[MAX_M];

/* subroutines */

template <typename T>
T gcd(T m, T n) {  // m >= 0, n >= 0
  if (m < n) swap(m, n);
  while (n > 0) {
    T r = m % n;
    m = n;
    n = r;
  }
  return m;
}

void normalize(int &x, int &y) {
  if (x == 0) y = 1;
  else if (y == 0) x = 1;
  else if (x < 0) x = -x, y = -y;
}

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d%d", xs + i, ys + i);

  mtp4i ecs;
  int m = 0;
  for (int i = 0; i < n; i++)
    for (int j = i + 1; j < n; j++) {
      int cx = xs[i] + xs[j], cy = ys[i] + ys[j];
      int dx = xs[j] - xs[i], dy = ys[j] - ys[i];
      if (dx == 0) dy = 1;
      int g = gcd(abs(dx), abs(dy));
      if (g > 1) dx /= g, dy /= g;
      normalize(dx, dy);

      tp4 e(cx, cy, dx, dy);
      ecs[e]++;
      es[m++] = e;
    }

  ll sum = 0;
  for (int i = 0; i < m; i++) {
    auto [cx, cy, dx, dy] = es[i];
    int rx = -dy, ry = dx;
    normalize(rx, ry);

    auto mit = ecs.find(tp4(cx, cy, rx, ry));
    if (mit != ecs.end()) sum += mit->second;
  }

  printf("%lld\n", sum / 2);
  
  return 0;
}