#include <fstream>
#include<cmath>
#include<algorithm>
using namespace std;
ifstream f("patrate3.in");
ofstream g("patrate3.out");
int n,i,j,nr;
#define E 0.0000000001

struct puncte {
    double x,y;}v[1010];

bool compar(puncte a,puncte b)
{
    if(fabs(a.x-b.x)<=E)
        return a.y<b.y;
    else
    return a.x<b.x;
}

int cautare(puncte a)
{
    int l,r,mij;
    l=1;
    r=n;
    while(l<=r)
    {
        mij=(l+r)/2;
        if (fabs(v[mij].x-a.x)<=E&&fabs(v[mij].y-a.y)<=E)
            return 1;
        else
        if (compar(a,v[mij]))
            r=mij-1;
        else
        l=mij+1;
    }
    return 0;
}


int main()
{f>>n;
for(i=1;i<=n;i++)
    f>>v[i].x>>v[i].y;
sort(v+1,v+n+1,compar);
nr=0;
for(i=1;i<n;i++)
    for(j=i+1;j<=n;j++)
{
    puncte a,b;
    a.x = v[i].x + v[i].y - v[j].y;
    b.x = v[j].x + v[i].y - v[j].y;
    a.y = v[i].y + v[j].x - v[i].x;
    b.y = v[j].y + v[j].x - v[i].x;
    if(cautare(a)&&cautare(b))
        nr++;
}
g<<nr/2;
return 0;
}