#include<stdio.h>
#include<algorithm>

struct coord
    {int x,y;};

coord v[1001];
double vec[1000001],nr1,nr2;

using namespace std;

int main()

{

freopen("trapez.in","r",stdin);
freopen("trapez.out","w",stdout);

int nrd=0,nrt=0,n,i,j,cate=0;

scanf("%d",&n);

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

for(i=1;i<=n;i++){
    for(j=i+1;j<=n;j++){
        nrd++;
        nr1=v[j].y-v[i].y;
        nr2=v[j].x-v[i].x;
        vec[nrd]=1.0*(nr1/nr2);}}

sort(vec+1,vec+nrd+1);

for(i=1;i<=nrd;i++){
    cate=1;
    while(vec[i]==vec[i+1]&&i+1<=nrd){
        cate++;
        i++;}
    nrt+=cate*(cate-1)/2;}

printf("%d",nrt);
return 0;
}