#include <iostream>
#include <cmath>
#include <set>
#include <fstream>
using namespace std;
ifstream f("patrate3.in");
ofstream g("patrate3.out");
const double EPS=1e-5;
int n,cate;
struct punct {
    double x,y;
} P[1001];
struct cmp {
    bool operator()(const punct &a, const punct &b) const {
        if(abs(a.x-b.x)>EPS) {
            return a.x < b.x;
        }
        if(abs(a.y-b.y)>EPS) {
            return a.y<b.y;
        }
        return 0;
    }
};
set<punct,cmp>da;


int main() {
    f>>n;
    for(int i=1; i<=n; i++) {
        f>>P[i].x>>P[i].y;
        da.insert(P[i]);
    }
    for(int i=1; i<=n; i++) {
        punct mij,cs,cd;
        for(int j=i+1; j<=n; j++) {
            mij.x=(P[i].x+P[j].x)/2;
            mij.y=(P[i].y+P[j].y)/2;
            cd.x=mij.y-P[j].y+mij.x;
            cd.y=P[j].x-mij.x+mij.y;
            cs.x=P[j].y-mij.y+mij.x;
            cs.y=mij.x-P[j].x+mij.y;
            if(da.find(cd)!=da.end()&&da.find(cs)!=da.end()) {
                cate++;
            }
        }
    }
    g<<cate/2;
    f.close();
    g.close();
    return 0;
}