#include<iostream>
#include<algorithm>
#include<queue>
#include<map>
#include<string.h>
#include <stdio.h>
#include<math.h>
#include<functional>

#define INTMAX_MAX 10000
#define INTMAX_MIN -10000

using namespace std;



int main(){
    
    
    int count = 0;
    pair<double, double> xy[100];
    while(cin>>count){
        
        if(count==0)break;
        for(int i=0; i<count; i++)scanf("%lf,%lf",&xy[i].first,&xy[i].second);
        sort(xy,xy+count);
        int now = 0;
        int end = count;
        while(now<end-1){
            double max = INTMAX_MIN;
            int max_n = now;
            for(int i=now+1; i<end; i++){
                double temp;
                double x = xy[i].first-xy[now].first;
                double y = xy[i].second-xy[now].second;
                if(x==0){
                    if(y>0)temp=INTMAX_MAX;
                    else temp= INTMAX_MIN+1;
                }else{
                    temp = y/x;
                }
                if(temp>max){
                    max = temp;
                    max_n = i;
                }
            }
            now = max_n;
            count--;
        }
        now = 0;
        while(now<end-1){
            double min = INTMAX_MAX;
            int min_n = now;
            for(int i=now+1; i<end; i++){
                double temp;
                double x = xy[i].first-xy[now].first;
                double y = xy[i].second-xy[now].second;
                if(x==0){
                    if(y>0)temp=INTMAX_MAX-1;
                    else temp= INTMAX_MIN;
                }else{
                    temp = y/x;
                }
                if(temp<min){
                    min = temp;
                    min_n = i;
                }
            }
            now = min_n;
            count--;
        }
        cout<<count<<endl;
        
        
    }
    
    
    

        


}