#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include <algorithm>
#include <atcoder/all>
#include <bitset>
#include <cassert>
#include <cmath>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n) - 1; i >= 0; i--)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define mod1 1000000007
#define mod2 998244353
#define mod3 100000007
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vector<int>>
#define vvc vector<vector<char>>
#define vvl vector<vector<ll>>
#define vvb vector<vector<bool>>
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define pii pair<int, int>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<ll, ll>>
#define vvpii vector<vector<pair<int, int>>>
#define vvpll vector<vector<pair<ll, ll>>>

using mint = modint998244353;

template <typename T>
void debug(T e) {
    cerr << e << endl;
}

template <typename T>
void debug(vector<T> &v) {
    rep(i, v.size()) { cerr << v[i] << " "; }
    cerr << endl;
}

template <typename T>
void debug(vector<vector<T>> &v) {
    rep(i, v.size()) {
        rep(j, v[i].size()) { cerr << v[i][j] << " "; }
        cerr << endl;
    }
}

template <typename T>
void debug(vector<pair<T, T>> &v) {
    rep(i, v.size()) { cerr << v[i].first << " " << v[i].second << endl; }
}

template <typename T>
void debug(set<T> &st) {
    for (auto itr = st.begin(); itr != st.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(multiset<T> &ms) {
    for (auto itr = ms.begin(); itr != ms.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(map<T, T> &mp) {
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        cerr << itr->first << " " << itr->second << endl;
    }
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << H << " ";
    debug_out(T...);
}

ll my_gcd(ll a, ll b) {
    ll ret = 0;
    if (a < b) {
        swap(a, b);
    }
    if (b == 0) {
        ret = a;
    } else {
        ret = my_gcd(b, a % b);
    }
    return ret;
}

int main() {
    ll N;
    cin >> N;
    vector<ll> x(N);
    vector<ll> y(N);
    for (ll i = 0; i < N; i++) {
        cin >> x[i] >> y[i];
    }
    // 傾きと中央の点の座標の組を持つ
    map<pair<pll, pll>, ll> mp;
    for (ll i = 0; i < N; i++) {
        for (ll j = i + 1; j < N; j++) {
            ll fx = x[j] - x[i];
            ll fy = y[j] - y[i];
            ll cx = x[i] + x[j];
            ll cy = y[i] + y[j];
            if (fx == 0) {
                pll p = pll(0, 1);
                pll c = pll(cx, cy);
                mp[pair<pll, pll>(p, c)]++;
            } else if (fy == 0) {
                pll p = pll(1, 0);
                pll c = pll(cx, cy);
                mp[pair<pll, pll>(p, c)]++;
            } else {
                ll g = my_gcd(abs(fx), abs(fy));
                fx /= g;
                fy /= g;
                if (fx < 0) {
                    fx *= -1;
                    fy *= -1;
                }
                pll p = pll(fx, fy);
                pll c = pll(cx, cy);
                mp[pair<pll, pll>(p, c)]++;
            }
        }
    }
    ll ans = 0;
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        ll px = (itr->first).first.first;
        ll py = (itr->first).first.second;
        ll cx = (itr->first).second.first;
        ll cy = (itr->first).second.second;
        //  debug_out(px, py, cx, cy, itr->second);

        if (px == 0) {
            pll p = pll(1, 0);
            pll c = pll(cx, cy);
            ans += itr->second * mp[pair<pll, pll>(p, c)];
        } else if (py == 0) {
            pll p = pll(0, 1);
            pll c = pll(cx, cy);
            ans += itr->second * mp[pair<pll, pll>(p, c)];
        } else {
            if (py < 0) {
                py *= -1;
                px *= -1;
            }
            pll p = pll(py, -px);
            pll c = pll(cx, cy);
            ans += itr->second * mp[pair<pll, pll>(p, c)];
        }
    }
    cout << ans / 2 << endl;
}