#include<fstream>
#include<algorithm>
using namespace std;
ifstream f("patrate3.in");
ofstream g("patrate3.out");
int N,nrt;
struct point { double x,y; }a[1001];
bool cmp(point a,point b)
{	if(a.x<b.x) return 1;
	if(a.x==b.x && a.y<b.y) return 1;
	return 0;
}
bool bin_search(point s)
{	int left,right,mid;
	left=1 , right=N;
	while(left<=right)
	{	mid=(left+right)>>1;
		if(a[mid].x==s.x && a[mid].y==s.y) return 1;
		if(s.x<a[mid].x || s.y<a[mid].y) right=mid-1;
		else if(a[mid].x<s.x || a[mid].y<s.y) left=mid+1;
	}
	return 0;
}
int main()
{	int i,j;
	point b,d;
	f>>N;
	for(i=1;i<=N;i++)
		f>>a[i].x>>a[i].y;
	sort(a+1,a+N+1,cmp);
	for(i=1;i<=N;i++)
		for(j=i+1;j<=N;j++)
		{	d.x=(a[i].x+a[j].x+a[i].y-a[j].y)/2;
			d.y=(a[i].y+a[j].y+a[j].x-a[i].x)/2;
			if(!bin_search(d)) continue;
			b.x=(a[i].x+a[j].x+a[j].y-a[i].y)/2;
			b.y=(a[i].y+a[j].y+a[i].x-a[j].x)/2;
			if(!bin_search(b)) continue;
			nrt++;
		}
	g<<nrt/2;
	f.close();
	g.close();
	return 0;
}