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

int a[1002],b[1002],pa,k,n;
double p[1000003];
int main()
{
    freopen("trapez.in","r",stdin);
    freopen("trapez.out","w",stdout);
    scanf("%d",&n);
    for(int i=1;i<=n;++i)scanf("%d%d",&a[i],&b[i]);
    for(int i=1;i<n;++i)
        for(int j=i+1;j<=n;++j)
            k++,p[k]=(double)(a[i]-a[j])/(b[i]-b[j]);
    sort(p+1,p+k+1);
    for(int i=1;i<=k;++i)
    {
        nr=1;
        while(p[i]==p[i+1]&&i+1<=k)++nr,++i;
        pa=pa+(nr-1)*nr/2;
    }
    printf("%d",pa);
    fclose(stdin);fclose(stdout);
    return 0;
}