#import<fstream>
#import<algorithm>
using namespace std;ifstream f("trapez.in");ofstream g("trapez.out");double p[999999];int n,m,i,j,s,x[999],y[999],nr;int main(){f>>n;for(i=1;i<=n;i++)f>>x[i]>>y[i];for(i=1;i<=n;i++)for(j=i+1;j<=n;j++)p[++m]=(double)(x[i]-x[j])/(y[i]-y[j]);sort(p+1,p+m+1);for(i=1;i<=m;i++){nr=1;while(p[i]==p[i+1]&&i+1<=m)nr++,i++;s+=(nr-1)*nr/2;}g<<s;}