#include<iostream>
#include<cstdio>
#include<vector>
#include<algorithm>
#include<map>
using namespace std;
#define X first
#define Y second
int main(){
  vector<pair<double,double> > pin;
  bool f[100];
  int n;
  while(cin >>n,n){
    pin.clear();
    for(int i=0; i<n; i++) f[i] = true;
    for(int i=0; i<n; i++){
      double a,b;
      scanf("%lf,%lf",&a,&b);
      pin.push_back(make_pair(a,b));
    }
    sort(pin.begin(),pin.end());
    int now = 0,next,ans = 0;
    for(;;){
      for(int i=0; i<n; i++){
	if(i == now || !f[i]) continue;
	next = i;
	double ax = pin[i].X-pin[now].X;
	double ay = pin[i].Y-pin[now].Y;
	for(int j=0; j<n; j++){
	  if(!f[j] || i == j) continue;
	  double bx = pin[j].X-pin[now].X;
	  double by = pin[j].Y-pin[now].Y;
	  if(ax*by-ay*bx<0){next = -1;break;}
	}
	if(next == i) break;
      }
      now = next;
      f[now] = false;
      if(now == 0) break;
    }
    for(int i=0; i<n; i++) if(f[i]) ans++;
    cout <<ans<<endl;
  }
  return 0;
}