#include<fstream>
#include<set>
#include<cmath>
const std::string txt="patrate3";
std::ifstream cin(txt+".in");
std::ofstream cout(txt+".out");
struct mtcmt{
    double x,y;
    mtcmt(int a=0,int b=0){
        x=a;y=b;}
    bool operator<(const mtcmt &z) const{
        return x<z.x || (x==z.x && y<z.y);
    }
}v[1005];
std::set <mtcmt> u;
signed main(int n,int r,double x,double y){
    cin>>n;
    for(int i=1;i<=n;++i){
        cin>>x>>y;
        x=round(x*10000);
        y=round(y*10000);
        v[i]=mtcmt(x,y);
        u.insert(v[i]);
    }
    r=0;
    for(int i=1;i<n;++i){
        for(int j=i+1;j<=n;++j){
            int mx=(v[i].x+v[j].x)/2;
            int my=(v[i].y+v[j].y)/2;
            int cx=mx-v[i].x;
            int cy=my-v[i].y;
            mtcmt v1(mx-cy,my+cx);
            mtcmt v2(mx+cy,my-cx);
            if(u.find(v1)!=u.end() && u.find(v2)!=u.end())
                ++r;
        }
    }
    cout<<r/2;
}