#define EPS 0.000001
#include <math.h>
#include <fstream.h>
//using namespace std;
int n;
double x[1001],y[1001];
void citire(){
ifstream fin("patrate3.in");
fin>>n;
for (int i=0;i<n;i++)
   fin>>x[i]>>y[i];
fin.close();
}
void bule(){
int ok=1,p=n;
while(ok){
ok=0;
p--;
for (int i=0;i<p;i++)
   if (x[i]>x[i+1]){
   double aux=x[i];
   x[i]=x[i+1];
   x[i+1]=aux;
   aux=y[i];
   y[i]=y[i+1];
   y[i+1]=aux;
   ok=1;
   }
}
}

int da(double a,double b,int m){
if (fabs(x[m]-a)<=EPS && fabs(y[m]-b)<=EPS)
  return 1;
return 0;
}

double binar(double a,double b,int p,int u){
if (p>u)
  return 0;
int m=(p+u)/2;
if  (da(a,b,m))
     return 1;
if (x[m]<a)
    return binar(a,b,m+1,u);
return binar(a,b,p,m-1);
}

long numarare(){
long nr=0;
for (int i=0;i<n-1;i++)
   for (int j=i+1;j<n;j++){
      if (binar(x[j]+(y[i]-y[j]),y[j]+(x[j]-x[i]),i,n)==1)
	if (binar(x[i]+(y[i]-y[j]),y[i]+(x[j]-x[i]),i,n)==1){
	   nr++;
	   break;}
   }
return nr;
}
int main(){
citire();
bule();
ofstream fout("patrate3.out");
fout<<numarare()<<"\n";
fout.close();
return 0;
}