#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
struct P
{
    double x,y;
};
P a[1501];
int i,n,j;
double r;
long long k;
int C(P a,P b)
{
    return a.x<b.x||(a.x==b.x&&a.y<b.y);
}
int bin(int p,int q,double c,double d)
{
    int m=(p+q)/2;
    if(p>q)
        return 0;
    if(fabs(c-a[m].x)<0.001&&fabs(d-a[m].y)<0.001)
        return m;
    if(a[m].x<c)
        return bin(m+1,q,c,d);
    return bin(p,m-1,c,d);
}
int main()
{
    freopen("triang.in","r",stdin);
    freopen("triang.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        scanf("%lf%lf",&a[i].x,&a[i].y);
    sort(a+1,a+n+1,C),r=sqrt(3);
    for(i=1;i<n-1;i++)
    for(j=i+1;j<n;j++)
    {
        if(bin(j+1,n,(a[i].x+a[j].x)/2+r*(a[i].y-a[j].y)/2,(a[i].y+a[j].y)/2+r*(a[j].x-a[i].x)/2))
             k++;
        if(bin(j+1,n,(a[i].x+a[j].x)/2+r*(a[j].y-a[i].y)/2,(a[i].y+a[j].y)/2+r*(a[i].x-a[j].x)/2))
             k++;
    }
    printf("%lld",k);
    return 0;
}