#include<bits/stdc++.h>

#define maxn 505

//#define LOCAL

using namespace std;

struct Point{

    int x,y;

    Point(int a = ,int b = ){

        x = a,y = b;

    }

    Point operator+ (const Point& p){

        return Point(x + p.x,y + p.y);

    }

    Point operator- (const Point& p){

        return Point(x - p.x,y - p.y);

    }

    bool operator== (const Point& p) const{

        return x == p.x && y == p.y;

    }

    bool operator< (const Point& p) const{

        if(x != p.x) return x < p.x;

        return y < p.y;

    }

};

struct line{

    Point s,t;

    line(){}

    line(Point a,Point b){

        s = a,t = b;

    }

    bool operator< (const line& l) const{

        if(!(s == l.s)) return s < l.s;

        return t < l.t;

    }

};

set<line> st;

Point store[maxn * maxn];

int main(){

    #ifdef LOCAL

    freopen("kkk.txt","r",stdin);

    freopen("kkkout.txt","w",stdout);

    #endif

    int n;

    while(scanf("%d",&n) == ){

        st.clear();

        for(int i = ;i < n;++i)

            scanf("%d%d",&store[i].x,&store[i].y);

        sort(store,store + n);

        for(int i = ;i < n;++i){

            for(int j = i + ;j < n;++j){

                st.insert(line(store[i],store[j]));

            }

        }

        int ans = ;

        for(int i = ;i < n;++i){

            for(int j = i + ;j < n;++j){

                Point d = store[j] - store[i];

                Point temp(d.y,-d.x);

                Point s = store[i] + temp;

                Point t = s + d;

                if(st.count(line(s,t))) ++ans;

            }

        }

        printf("%d\n",ans / );

    }

    return ;

}