You are given n points on a plane. All the points are distinct and no three of them lie on the same line. Find the number of parallelograms with the vertices at the given points.

Input

The first line of the input contains integer n (1 ≤ n ≤ 2000) — the number of points.

Each of the next n lines contains two integers (xi, yi) (0 ≤ xi, yi ≤ 109) — the coordinates of the i-th point.

Output

Print the only integer c — the number of parallelograms with the vertices at the given points.

Example

Input

4
0 1
1 0
1 1
2 0


Output

1
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const ll MOD = 998244353;
const int INF = (ll)1e9 + 7;
const ll INFLL = (ll)1e18;
template <class t>
using vvector = vector<vector<t>>;
template <class t>
using vvvector = vector<vector<vector<t>>>;
template <class t>
using priority_queuer = priority_queue<t, vector<t>, greater<t>>;
template <class t, class u>
bool chmax(t &a, u b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class t, class u>
bool chmin(t &a, u b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
namespace templates {
ll modpow(ll x, ll b) {
  ll res = 1;
  while (b) {
    if (b & 1) res = res * x % MOD;
    x = x * x % MOD;
    b >>= 1;
  }
  return res;
}
ll modinv(ll x) { return modpow(x, MOD - 2); }
bool was_output = false;
template <class t>
void output(t a) {
  if (was_output) cout << " ";
  cout << a;
  was_output = true;
}
void outendl() {
  was_output = false;
  cout << endl;
}
ll in() {
  ll res;
  cin >> res;
  return res;
}
template <class t>
istream &operator>>(istream &is, vector<t> &x) {
  for (auto &i : x) is >> i;
  return is;
}
template <class t, class u>
istream &operator>>(istream &is, pair<t, u> &x) {
  is >> x.first >> x.second;
  return is;
}
template <class t>
t in() {
  t res;
  cin >> res;
  return res;
}
template <class t>
void out(t x) {
  cout << x;
}
template <class t>
vector<t> sorted(
    vector<t> line,
    function<bool(t, t)> comp = [](t a, t b) { return a < b; }) {
  sort(line.begin(), line.end(), comp);
  return line;
}
template <class t>
vector<t> reversed(vector<t> line) {
  reverse(line.begin(), line.end());
  return line;
}
}  // namespace templates
using namespace templates;
pii operator+(pii a, pii b) {
  return pii(a.first + b.first, a.second + b.second);
}
pii operator-(pii a, pii b) {
  return pii(a.first - b.first, a.second - b.second);
}
pii complete(pii a) {
  if (a.second < 0) {
    a.first = -a.first;
    a.second = -a.second;
  }
  if (a.first < 0) {
    a.first = -a.first;
    a.second = -a.second;
  }
  return a;
}
ll func() {
  std::cin.tie(nullptr);
  std::ios_base::sync_with_stdio(false);
  int n = in();
  vector<pii> line(n);
  for (auto &i : (line)) i = in<pii>();
  map<pii, ll> m;
  for (int i = (n) * (strlen("") != 0); i < (int)(strlen("") ?: (n)); ++i) {
    for (int j = (i + 1) * (strlen("n") != 0);
         j < (int)(strlen("n") ? n : (i + 1)); ++j) {
      ++m[complete(line[j] - line[i])];
    }
  }
  ll res = 0;
  for (auto &i : (m)) {
    res += i.second * (i.second - 1) / 2;
  }
  return res / 2;
}
int main() {
  cout << func() << endl;
  return 0;
}
