#include<bits/stdc++.h>
#include<atcoder/all>
#define rep(i,b) for(int i=0;i<b;i++)
#define rrep(i,b) for(int i=b-1;i>=0;i--)
#define rep1(i,b) for(int i=1;i<b;i++)
#define repx(i,x,b) for(int i=x;i<b;i++)
#define rrepx(i,x,b) for(int i=b-1;i>=x;i--)
#define fore(i,a) for(auto& i:a)
#define rng(x) (x).begin(), (x).end()
#define rrng(x) (x).rbegin(), (x).rend()
#define sz(x) ((int)(x).size())
#define pb push_back
#define fi first
#define se second
#define pcnt __builtin_popcountll

using namespace std;
using namespace atcoder;

using ll = long long;
using ull = long long;
using ld = long double;
template<typename T> using mpq = priority_queue<T, vector<T>, greater<T>>;
template<typename T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<typename T> bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<typename T> ll sumv(const vector<T>&a){ll res(0);for(auto&&x:a)res+=x;return res;}
bool yn(bool a) { if(a) {cout << "Yes" << endl; return true;} else {cout << "No" << endl; return false;}}
#define retval(x) {cout << #x << endl; return;}
#define cout2(x,y) cout << x << " " << y << endl;
#define coutp(p) cout << p.fi << " " << p.se << endl;
#define out cout << ans << endl;
#define outd cout << fixed << setprecision(20) << ans << endl;
#define outm cout << ans.val() << endl;
#define outv fore(yans , ans) cout << yans << "\n";
#define outdv fore(yans , ans) cout << yans.val() << "\n";
#define assertmle(x) if (!(x)) {vi v(3e8);}
#define asserttle(x) if (!(x)) {while(1){}}
#define coutv(v) {fore(vy , v) {cout << vy << " ";} cout << endl;}
#define coutv2(v) fore(vy , v) cout << vy << "\n";
#define coutvm(v) {fore(vy , v) {cout << vy.val() << " ";} cout << endl;}
#define coutvm2(v) fore(vy , v) cout << vy.val() << "\n";
using pll = pair<ll,ll>;using pil = pair<int,ll>;using pli = pair<ll,int>;using pii = pair<int,int>;using pdd = pair<ld,ld>;
using vi = vector<int>;using vd = vector<ld>;using vl = vector<ll>;using vs = vector<string>;using vb = vector<bool>;
using vpii = vector<pii>;using vpli = vector<pli>;using vpll = vector<pll>;using vpil = vector<pil>;
using vvi = vector<vector<int>>;using vvl = vector<vector<ll>>;using vvs = vector<vector<string>>;using vvb = vector<vector<bool>>;
using vvpii = vector<vector<pii>>;using vvpli = vector<vector<pli>>;using vvpll = vector<vpll>;using vvpil = vector<vpil>;
using mint = modint998244353;
//using mint = modint1000000007;
//using mint = dynamic_modint<0>;
using vm = vector<mint>;
using vvm = vector<vector<mint>>;
vector<int> dx={1,0,-1,0,1,1,-1,-1},dy={0,1,0,-1,1,-1,1,-1};
ll gcd(ll a, ll b) { return a?gcd(b%a,a):b;}
ll lcm(ll a, ll b) { return a/gcd(a,b)*b;}
#define yes {cout <<"Yes"<<endl;}
#define no {cout <<"No"<<endl;}
const double eps = 1e-10;
const ll LINF = 2001002003004005006ll;
const int INF = 1001001001;
#ifdef MY_LOCAL_DEBUG
#include "./debug/localDebug.cpp"
#define showp(p) cerr<<#p<<" = "<<p.fi<<" : "<<p.se<<endl
#define show1(a) cerr<<#a<<" = "<<a<<endl
#define show2(a,b) cerr<<#a<<" = "<<a<<" : "<<#b<<" = "<<b<<endl
#define show3(a,b,c) cerr<<#a<<" = "<<a<<" : "<<#b<<" = "<<b<<" : "<<#c<<" = "<<c<<endl
#define show4(a,b,c,d) cerr<<#a<<" = "<<a<<" : "<<#b<<" = "<<b<<" : "<<#c<<" = "<<c<<" : "<<#d<<" = "<<d<<endl
#define show5(a,b,c,d,e) cerr<<#a<<" = "<<a<<" : "<<#b<<" = "<<b<<" : "<<#c<<" = "<<c<<" : "<<#d<<" = "<<d<<" : "<<#e<<" = "<<e<<endl
#define DEBUG_LINE cout << "DEBUG_LINE : " << __LINE__ << endl
#define showv(v) {cout<<#v<<" : "; fore(vy , v) {cout << vy << " ";} cout << endl;}
#define showv2(v) {cout<<#v<<endl; fore(vy , v) cout << vy << "\n";}
#define showvm(v) {cout<<#v<<" : "; fore(vy , v) {cout << vy.val() << " ";} cout << endl;}
#define showvm2(v) {cout<<#v<<endl; fore(vy , v) cout << vy.val() << "\n";}
#define showmat(v) {cout<<#v<<endl; fore(row , v) { fore(seg , row) cout << seg << " "; cout << endl;}}
#define showmatm(v) {cout<<#v<<endl; fore(row , v) { fore(seg , row) cout << seg.val() << " "; cout << endl;}}
#else
#define showp(p)
#define show1(a)
#define show2(a,b)
#define show3(a,b,c)
#define show4(a,b,c,d)
#define show5(a,b,c,d,e)
#define DEBUG_LINE
#define showv(v)
#define showv2(v)
#define showvm(v)
#define showvm2(v)
#define showmat(v)
#define showmatm(v)
#endif
#define overload5(a,b,c,d,e,f, ...) f
#define show(...) overload5(__VA_ARGS__, show5, show4, show3, show2, show1)(__VA_ARGS__)

// 偏角モード
// #define DECLINATION 
        
struct rational{
    ll num; // 分子
    ll den; // 分母
#if defined(DECLINATION)
    int quad; // 第1象限～4象限(境界上に注意)
#endif

    rational(){
        // とりあえず許す
        // どの値で初期化すべきかわかっていない
        num = 0;
        den = 0;
    }  

    rational(ll num_, ll den_){
        assert(num_ != 0 || den_ != 0);
#if defined(DECLINATION)
        if     (den_ >= 0 && num_ >  0) quad = 1;
        else if(den_ <  0 && num_ >= 0) quad = 2;
        else if(den_ <= 0 && num_ <  0) quad = 3;
        else if(den_ >  0 && num_ <= 0) quad = 4;
        if (num_ == 0){
            num = 0;
            den = 1;
            if (den_ < 0) den *= -1;
        }else if(den_ == 0){
            num = 1;
            if (num_ < 0) num *= -1;
            den = 0;
        }else{
            ll d = gcd(abs(num_),abs(den_));
            num = num_/d;
            den = den_/d;
        }
#else
        if (num_ == 0){
            num = 0;
            den = 1;
        }else if(den_ == 0){
            num = 1;
            den = 0;
        }else{
            ll d = gcd(abs(num_),abs(den_));
            num = abs(num_)/d;
            den = abs(den_)/d;
            if((num_ < 0 && den_ > 0) || (num_ > 0 && den_ < 0)) num *= -1;
        }
#endif
    }

    rational(const rational& other) : num(other.num), den(other.den) {
#if defined(DECLINATION)
        quad = other.quad;
#endif
}

    rational& operator=(const rational& other) {
    if (this != &other) { // 自己代入でないことを確認
        num = other.num;
        den = other.den;
#if defined(DECLINATION)
        quad = other.quad;
#endif
    }
    return *this;
}

#if !defined(DECLINATION)
    rational operator+(const rational& other) const{
        if (den == 0 || other.den == 0) return rational(1,0);
        assert(abs(other.num) < LLONG_MAX/abs(den));
        assert(abs(num) < LLONG_MAX/abs(other.den));
        return rational(num*other.den + den*other.num, den*other.den);
    }
    rational operator-(const rational& other) const{
        return *this + rational(other.num,-other.den);
    }
    rational operator*(const rational& other) const{
        if (den == 0 || other.den == 0) return rational(1,0);
        if (other.num == 0) return rational(0,1);
        assert(abs(num) < LLONG_MAX/abs(other.num));
        assert(abs(other.den) < LLONG_MAX/abs(den));
        return rational(num*other.num, den*other.den);
    }
    rational operator/(const rational& other) const{
        return *this * rational(other.den , other.num);
    }
    rational& operator+=(const rational& other){
        *this = *this + other;
        return *this;
    }
    rational& operator-=(const rational& other){
        *this = *this - other;
        return *this;
    }
    rational& operator*=(const rational& other){
        *this = *this * other;
        return *this;
    }
    rational& operator/=(const rational& other){
        *this = *this / other;
        return *this;
    }
    rational operator+(const ll& other) const{
        return *this + rational(other,1);
    }
    rational operator-(const ll& other) const{
        return *this - rational(other,1);
    }
    rational operator*(const ll& other) const{
        return *this * rational(other,1);
    }
    rational operator/(const ll& other) const{
        return *this / rational(other,1);
    }
    rational& operator+=(const ll& other){
        *this = *this + other;
        return *this;
    }
    rational& operator-=(const ll& other){
        *this = *this - other;
        return *this;
    }
    rational& operator*=(const ll& other){
        *this = *this * other;
        return *this;
    }
    rational& operator/=(const ll& other){
        *this = *this / other;
        return *this;
    }
#endif // !defined(DECLINATION)
    rational operator+() const{
        return *this;
    }
    rational operator-() const{
        return rational(0,1) - *this;
    }

    bool operator==(const rational& other) const{
        return (num == other.num) && (den == other.den);
    }
    bool operator!=(const rational& other) const{
        return (num != other.num) || (den != other.den);
    }
    bool operator<(const rational& other) const{
        if (abs(other.den)) assert(abs(num) < LLONG_MAX/abs(other.den));
        if (abs(den)) assert(abs(other.num) < LLONG_MAX/abs(den));
#if defined(DECLINATION)
        if (quad != other.quad){
            return ((quad+1)%4 < (other.quad+1)%4);
        }
#endif // defined(DECLINATION)
        return num*other.den < den*other.num;
    }
    bool operator<=(const rational& other) const{
        if (*this == other) return true;
        else return (*this < other);
    }
    bool operator>(const rational& other) const{
        return !(*this <= other);
    }
    bool operator>=(const rational& other) const{
        return !(*this < other);
    }
};

struct line{
    rational grad;
    rational y_intercept;
    rational x_intercept;

    line(ll x1, ll y1, ll x2, ll y2){
        assert(x1!=x2 || y1!=y2);
        grad = rational(y2-y1, x2-x1);
        y_intercept = -grad * x1 + y1;
        x_intercept = -rational(x2-x1, y2-y1) * y1 + x1;
    }

    bool operator<(line const other) const{
        if (grad != other.grad) return grad < other.grad;
        if (y_intercept != other.y_intercept) return y_intercept < other.y_intercept;
        if (x_intercept != other.x_intercept) return x_intercept < other.x_intercept;
        return false;
    }
};

// rational
// [remark]
// 有理数クラス
// 偏角の大小を扱いたい場合はDECLINATIONを定義する。この場合四則演算は定義されない。
// 分子が0となるとき分母は強制的に１となる。
// 分母が0となるとき分子は強制的に１となる。そのため、直線を扱いたい場合はlineクラスを使う。
// 四則演算 or 大小比較でオーバーフローが発生したときアサートで知らせる。
// 例えば、２回以上の四則演算や１回四則演算した後に大小比較を適用させる場合はオーバフローが発生する場合がある
//
// [interface]
// rational(a,b) : a/bを既約分数の状態で管理。DECLINATIONが定義されている場合は何象限かも管理。
//
// line
// [remark]
// 直線を有理数で扱うクラス。mapのキーに指定できる。
// ２点を通る直線を定義しその大小比較を行う。
// x_interceptなしでは、直線がy軸に平行な２直線の区別ができない。

void solve(){
    int n; cin>>n;
    vi x(n),y(n);
    rep(i,n) cin>>x[i]>>y[i];

    using prr = pair<rational, pll>;
    map<prr, ll> mp;
    rep(i,n) repx(j,i+1,n){
        rational l(x[i]-x[j], y[i]-y[j]);
        pll c(x[i]+x[j], y[i]+y[j]);
        prr p = {l, c};
        mp[p]++;
    }
    ll ans = 0;
    rep(i,n) repx(j,i+1,n){
        rational l(y[i]-y[j], x[j]-x[i]);
        pll c(x[i]+x[j], y[i]+y[j]);
        prr p = {l, c};
        ans += mp[p];
    }
    show(ans);
    ans /= 2;
    out;

    return;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    //cin>>t;

    rep(i,t){
        solve();
    }

    return 0;
}