#include <cstdio>
#include <cmath>
#include <algorithm>

using namespace std;

const double eps=1.e-4;

struct point{
    double x,y;
};

point v[1005];

bool cmp(point a,point b){
    if(fabs(a.x-b.x)<eps)   return a.y<b.y;
    return a.x<b.x;
}

bool binar(int n,point x){
    int st,dr,med;
    st=1;
    dr=n;
    while(st<=dr){
        med=st+(dr-st)/2;
        if(fabs(v[med].x-x.x)<eps && fabs(v[med].y-x.y)<eps)
            return 1;
        else
            if(cmp(x,v[med]))
                dr=med-1;
        else
            st=med+1;
    }
    return 0;
}

bool solve(point aux,point auy,int n){
    point a,b;
    
    a.x=auy.x+aux.y-auy.y;
    a.y=auy.y+auy.x-aux.x;
    b.x=aux.x+aux.y-auy.y;
    b.y=aux.y+auy.x-aux.x;
    
    if(binar(n,a)&&binar(n,b))
        return 1;
    return 0;
}

int main(){
    freopen("patrate3.in", "r", stdin);
    freopen("patrate3.out", "w", stdout);
    
    int n,i,j,sol=0;
    double x,y;
    
    scanf("%d",&n);
    
    for(i=1;i<=n;++i){
        scanf("%lf%lf",&x,&y);
        v[i].x=x;
        v[i].y=y;
    }
    
    sort(v+1,v+n+1,cmp);
    
    for(i=1;i<n;++i){
        for(j=i+1;j<=n;++j){
            sol+=solve(v[i],v[j],n);
        }
    }
    
    printf("%d\n",sol/2);
    
    return 0;
}