#include <cstdio>
#include <algorithm>
using namespace std;

struct punct{int x,y;};
punct v[1001];
punct panta[1000005];

int modul(int a)
{
    if(a<0)
        a=a*(-1);

    return a;
}

int cmmdc(int a, int b)
{
    int r;
    while(b!=0)
    {
        r=a%b;
        a=b;
        b=r;
    }

    return a;
}

bool cmp(punct a, punct b)
{
    if(a.x<b.y)
        return true;
    else if(a.x>b.x)
        return false;
    else if(a.y<b.y)
        return true;
    else
        return false;
}

int main(){
    freopen("trapez.in" , "r" , stdin);
    freopen("trapez.out" , "w" , stdout);
    int n,i,j,k,cate,sol;

    scanf("%d" , &n);

    for(i=1; i<=n; i++)
        scanf("%d%d" , &v[i].x, &v[i].y);

    sort(v, v+1, cmp);

    k=0;
    for(i=1;i<=n;i++)
        for(j=i+1;j<=n;j++)
        {
            k++;
            panta[k].x=modul(v[i].x-v[j].x);
            panta[k].y=modul(v[i].y-v[j].y);

            panta[k].x=panta[k].x/cmmdc(panta[k].x, panta[k].y);
            panta[k].y=panta[k].y/cmmdc(panta[k].x, panta[k].y);
        }

    sort(panta, panta+k+1, cmp);

    cate=1; sol=0;
    for(i=1; i<=k; i++)
        if(panta[i].x==panta[i+1].x && panta[i].y==panta[i+1].y)
            cate++;
        else
        {
            sol=sol+cate*(cate-1)/2;
            cate=1;
        }
    sol=sol+cate*(cate-1)/2;

    printf("%d" , sol);

    return 0;
}