#include<iostream>
#include<fstream>
#include<vector>
#include<math.h>
#include<algorithm>
using namespace std;
#define mod 1001
const double eps = 0.0001;
struct punct {
	long double x,y;
};
vector <punct> v[mod];
punct a[1001];
inline int compara(punct a, punct b)
{
	if(fabs(a.x-b.x)>eps)
		return 0;
	if(fabs(a.y-b.y)>eps)
		return 0;
	return 1;
}
inline void adauga(punct x)
{
	int k;
	k=(int)(x.x+x.y)%mod;
	if(k<0)
		k=-k;
	v[k].push_back(x);
}
inline int cauta(punct x)
{
	int n,i,k;
	k=(int)(x.x+x.y)%mod;
	if(k<0)
		k=-k;
	n=v[k].size()-1;
	for(i=0;i<=n;i++) 
		if(compara(v[k][i],x))
			return 1;
	return 0;
}
int main ()
{
	int n,i,j,nr;
	punct x,y,d,mij;
	ifstream f("patrate3.in");
	ofstream g("patrate3.out");
	f>>n;
	for(i=1;i<=n;i++) {
		f>>a[i].x>>a[i].y;
		adauga(a[i]);
	}
	f.close();
	nr=0;
	for(i=1;i<n;i++) 
		for(j=i+1;j<=n;j++) {
			mij.x=a[i].x+a[j].x;
			mij.x=mij.x/2;
            mij.y=a[i].y+a[j].y;
			mij.y=mij.y/2;
            d.x=mij.x-a[i].x;
            d.y=mij.y-a[i].y;
			if(a[i].y<a[j].y) {
				x.x=mij.x+d.y;
				x.y=mij.y-d.x;
				y.x=mij.x-d.y;
				y.y=mij.y+d.x;
			}
            else {
				x.x=mij.x-d.y;
				x.y=mij.y+d.x;
				y.x=mij.x+d.y;
				y.y=mij.y-d.x;
			}
			if((cauta(x))&&(cauta(y)))
				nr++;
		}
	g<<nr/2;
	g.close();
	return 0;
}