#include<iostream>
#include<string>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#define deb 0
using namespace std;
int main(void){
    int n;
    while(1){
        cin>>n;
        if(!n)break;
        double p[2][200];
        double xmin=10000.0;
        bool flg[200]={0};
        int xi,first;
        for(int i=0;i<n;i++){
            scanf("%lf,%lf",&p[0][i],&p[1][i]);
            if(xmin>p[0][i])xmin=p[0][i],first=xi=i;
            if(deb)cout<<"first="<<first<<endl;
        }
        if(deb)for(int i=0;i<n;i++){
            cout<<i<<" ... ("<<p[0][i]<<","<<p[1][i]<<")"<<endl;
        }
        if(deb)cout<<"."<<endl;
        double r=10000;
        double next=270,ith=1000,now=0;
        int nextnum,nextnow;
        int q=n;
        while(q--){
            if(deb)cout<<"next="<<next<<endl;
            for(int i=0;i<n;i++){
                if(!flg[i]&&i!=xi){
                    if(deb)cout<<i<<"******"<<endl;
                    double xd=p[0][i]-p[0][xi],yd=p[1][i]-p[1][xi];
                    double rd=hypot(xd,yd);
                    now=atan2(yd/rd,xd/rd)/M_PI*180;
                    if(now<0)now+=360;
                    if(deb)cout<<"xd="<<xd<<",yd="<<yd<<endl;
                    if(deb)cout<<"rd="<<rd<<endl;
                    if(deb)cout<<"atan2="<<now<<endl;
                    double fnow;
                    next-now<0 ? fnow=next-now+360:fnow=next-now;
                    if(deb)cout<<"next-now="<<fnow<<endl;
                    if(fnow<ith){
                        nextnum=i;
                        nextnow=now;
                        ith=fnow;
                        if(deb)cout<<"///"<<nextnum<<endl;
                    }
                }
            }
            flg[nextnum]=1;
            if(deb)cout<<"<"<<nextnum<<">"<<endl<<endl;
            xi=nextnum;
            next=nextnow;
            ith=1000;
            if(flg[first])break;
        }
        int f=0;
        for(int i=0;i<n;i++){
            if(!flg[i])f++;
            if(deb)cout<<"flg["<<i<<"] = "<<flg[i]<<endl;
        }
        cout<<f<<endl;
    }
    return 0;
}