#include<cstdio>
#include<algorithm>
using namespace std;
struct ab{int a,b;};
ab v[1001];
float a[500502];
bool sor(float a,float b)
{
    if(a>b)
        return false;
    return true;
}
int main()
{
    freopen("trapez.in","r",stdin);
    freopen("trapez.out","w",stdout);
    int n,i,j,h,ma,aa,ab,mi;
    float c;
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        scanf("%d%d",&v[i].a,&v[i].b);
    }
    int k=0;
    for(i=1;i<=n;i++)
    {
        for(j=i+1;j<=n;j++)
        {
            k++;
            aa=v[i].a-v[j].a;
            ab=v[i].b-v[j].b;
            a[k]=1.0*aa/ab;
        }
    }
    sort(a+1,a+k+1,sor);
    int e,s=0;
    for(i=1;i<k;)
    {
        c=a[i];
        e=0;
        while(c==a[i])
        {
            e++;
            i++;
        }
        if(e>=2)
            s+=e*(e-1)/2;
    }
    printf("%d",s);
    return 0;
}