ll@n,x[n],y[],d[],z=0;
double a[];
rd((x,y)(n));
rep(i,n){
	rep(j,n){
		if(i!=j){
			a[j]=atan2(y[j]-y[i],x[j]-x[i]);
		}
	}
	a[i]=a[n-1];
	sortA_index(n-1,a,d);
	rep(k,n-2){
		if(a[k]==a[k+1]){
			ll j1=d[k],j2=d[k+1];
			if(j1==i){
				j1=n-1;
			}
			if(j2==i){
				j2=n-1;
			}
			if((y[j1]-y[i])*(x[j2]-x[i])==(y[j2]-y[i])*(x[j1]-x[i])){
				z+=1;
				break;
			}
		}
	}
}
wt(z);