#include<cstdio>
#include<cmath>
#include<unordered_set>
#define eps 1.e-6
using namespace std;
struct POINT
{
     double x,y;
    inline bool operator==(const POINT &other) const
    {
        return fabs(x-other.x)<eps && fabs(y-other.y)<eps;
    }
} A,B,p[1010];
class HASH_POINT
{
    public: inline int operator()(const POINT &x) const
    {
        return int((x.x*1000)+x.y);
    }
};
unordered_set<POINT,HASH_POINT> q;
int n;
int main()
{
    freopen("patrate3.in","r",stdin);
    freopen("patrate3.out","w",stdout);
    int res=0;
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
        scanf("%lf%lf",&p[i].x,&p[i].y),
        q.insert(p[i]);
    for(int i=1;i<=n;i++)
        for(int j=i+1;j<=n ;j++)
            {
                A.x=p[i].x+p[i].y-p[j].y;
                A.y=p[i].y+p[j].x-p[i].x;
                B.x=p[i].y+p[j].x-p[j].y;
                B.y=p[j].x+p[j].y-p[i].x;
                if(q.find(A)!=q.end() && q.find(B)!=q.end())
                    res++;
            }
    printf("%d\n",res/2);
    return 0;
}