ll n,w,x[1000],y[1000],z[1000];
int ai[500000],aj[500000];ll ad[500000];
{
	rd(n,(x,y)(n));
	int k=0;
	rep(i,n)rep(j,i)ai[k]=i,aj[k]=j,ad[k]=(x[j]-x[i])**2+(y[j]-y[i])**2,++k;
	sortA(k,ad,ai,aj);
	rep(l,k){
		int i=ai[l];
		int j=aj[l];
		if(j==0){
			if(!z[i]){
				z[i]=1;
				w+=1;
			}
		}else{
			if(!z[i]&&!z[j]){
				z[i]=z[j]=1;
			}
		}
	}
	wt(w);
}