// (⁠◕⁠ᴗ⁠◕⁠✿⁠)

#include <bits/stdc++.h>
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define srep(i, s, n) for (ll i = s; i < (n); i++)
#define len(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
using namespace std;
template<typename T> using vc = vector<T>;
template<typename T> using vv = vc<vc<T>>;
template<typename T> using vvv = vv<vc<T>>;
using vi = vc<int>;using vvi = vv<int>; using vvvi = vv<vi>;
using ll = long long;using vl = vc<ll>;using vvl = vv<ll>; using vvvl = vv<vl>;
using ld = long double; using vld = vc<ld>; using vvld = vc<vld>; using vvvld = vc<vvld>;
using uint = unsigned int;
using ull = unsigned long long;
const ld pi = acos(-1.0);
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
// const ll mod = 1000000007;
const ll mod = 998244353;
inline bool inside(ll y, ll x, ll H, ll W) {return 0 <= (y) and (y) < (H) and 0 <= (x) and (x) < (W); }

#define debug(var)  do{std::cout << #var << " : \n";view(var);}while(0)
template<typename T> void view(T e){cout << e << endl;}
template<typename T> void view(const vc<T>& v){for(const auto& e : v){ cout << e << " "; } cout << endl;}
template<typename T> void view(const vv<T>& vv){ for(const auto& v : vv){ view(v); } }

int main(){
    int N; cin >> N;
    vl X(N), Y(N); rep(i, N) cin >> X[i] >> Y[i];
    rep(i, N){
        X[i] *= 2;
        Y[i] *= 2;
    }
    map<tuple<ll, ll, ll, ll>, ll> cnt;
    rep(j, N) rep(i, j){
        ll mx = (X[i] + X[j]) / 2, my = (Y[i] + Y[j]) / 2;
        ll p = (Y[i] - Y[j]), q = (X[i] - X[j]);
        if (q < 0){
            q = -q;
            p = -p;
        }
        if (p == 0) q = 1;
        else if (q == 0) p = 1;
        else{
            ll g = gcd(p, q);
            p /= g;
            q /= g;
        }
        if (!cnt.count({mx, my, p, q})) cnt[{mx, my, p, q}] = 0;
        cnt[{mx, my, p, q}]++;
    }
    ll ans = 0;
    for (auto [ele, c] : cnt){
        auto [mx, my, p, q] = ele;
        ll np = -q, nq = p;
        if (nq < 0){
            nq = -nq;
            np = -np;
        }
        if (np == 0) nq = 1;
        if (nq == 0) np = 1;
        if (cnt.count({mx, my, np, nq})) ans += c * cnt[{mx, my, np, nq}];
    }
    ans /= 2;
    cout << ans << endl;
}