#include <bits/stdc++.h>
using namespace std;
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("O3")
#pragma GCC target("avx")
const long long INF = numeric_limits<long long>::max();
const long double PI = 3.1415926535898;
const long long MOD = 1000000007;
const long long LIM = 100005;
long long fpow(long long x, long long y) {
  long long temp;
  if (y == 0) return 1;
  temp = fpow(x, y / 2);
  if (y % 2 == 0)
    return temp * temp;
  else
    return x * temp * temp;
}
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
bool isPrime(long long n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;
  for (long long i = 5; i * i <= n; i = i + 6)
    if (n % i == 0 || n % (i + 2) == 0) return false;
  return true;
}
long long modInverse(long long n, long long p) { return fpow(n, p - 2); }
map<long long, long long> primeFactors(long long n) {
  map<long long, long long> mp;
  while (n % 2 == 0) {
    if (mp.count(2) == 1)
      mp[2]++;
    else
      mp.insert({2, 1});
    n = n / 2;
  }
  for (long long i = 3; i <= sqrt(n); i = i + 2) {
    while (n % i == 0) {
      if (mp.count(i) == 1)
        mp[i]++;
      else
        mp.insert({i, 1});
      n = n / i;
    }
  }
  if (n > 2) {
    if (mp.count(n) == 1)
      mp[n]++;
    else
      mp.insert({n, 1});
  }
  return mp;
}
long long getDistance(pair<long long, long long> p1,
                      pair<long long, long long> p2) {
  return (p1.first - p2.first) * (p1.first - p2.first) +
         (p1.second - p2.second) * (p1.second - p2.second);
}
void solve() {
  long long n, ans = 0;
  cin >> n;
  vector<pair<long long, long long>> v(n);
  for (long long i = 0; i < n; i++) cin >> v[i].first >> v[i].second;
  map<long long, long long> mp;
  for (long long i = 0; i < n; i++) {
    for (long long j = i + 1; j < n; j++) {
      pair<long long, long long> p1 = v[i], p2 = v[j];
      if (p1.second > p2.second) swap(p1, p2);
      long double slp = atan2(p2.second - p1.second, p2.first - p1.first);
      if (p1.second == p2.second) slp = 0.0;
      long long dist = getDistance(v[i], v[j]);
      mp[slp * 1e15 + dist]++;
    }
  }
  for (long long i = 0; i < n; i++) {
    for (long long j = i + 1; j < n; j++) {
      pair<long long, long long> p1 = v[i], p2 = v[j];
      if (p1.second > p2.second) swap(p1, p2);
      long double slp = atan2(p2.second - p1.second, p2.first - p1.first);
      if (p1.second == p2.second) slp = 0.0;
      long long dist = getDistance(v[i], v[j]);
      ans += mp[slp * 1e15 + dist] - 1;
    }
  }
  assert(ans % 4 == 0);
  ans /= 4;
  cout << ans << "\n";
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  { solve(); }
  return 0;
}
