#include <fstream>
#include <cmath>

using namespace std;

int main()
{
    ifstream f("trapez.in");
    ofstream g("trapez.out");
    int n,i,j,k,m,c=0;
    f>>n;
    struct L {int x,y;};
    L p[n+1];
    for(i=1;i<=n;i++)
          f>>p[i].x>>p[i].y;
    for(i=1;i<=n-3;i++)
        for(j=i+1;j<=n-2;j++)
            for(k=j+1;k<=n-1;k++)
                for(m=k+1;m<=n;m++)
                    if(abs(p[j].y-p[m].y)/abs(p[j].x-p[m].x)==abs(p[i].y-p[k].y)/abs(p[i].x-p[k].x) &&
                       abs(p[j].y-p[i].y)/abs(p[j].x-p[i].x)!=abs(p[k].y-p[m].y)/abs(p[k].x-p[m].x))
                                         c++;
    g<<c;
    return 0;
}