#include<iostream>
#include<fstream>
#include<sstream>
#include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>

#include<stack>
#include<queue>
#include<set>
#include<map>
#include<vector>
#include<list>

#include<algorithm>
#include<utility>
#include<complex>

using namespace std;

#define reE(i,a,b) for(auto (i)=(a);(i)<=(b);(i)++)
#define rE(i,b) reE(i,0,b)
#define reT(i,a,b) for(auto (i)=(a);(i)<(b);(i)++)
#define rT(i,b) reT(i,0,b)
#define rep(i,a,b) reE(i,a,b);

#define rev(i,a,b) for(auto (i)=(b)-1;(i)>=(a);(i)--)
#define itr(i,b) for(auto (i)=(b).begin();(i)!=(b).end();++(i))
#define LL long long
#define all(b) (b).begin(),(b).end()


#define inpur_line(str,is) getline(cin, str);is.str(str);is.clear(istringstream::goodbit)
#define input_token(ss,is,token,num) ss.str(""); ss.clear(stringstream::goodbit); getline(is, token, ','); ss << token; ss >> num

typedef complex<double> P;
typedef vector<P> Poly;

const LL INF = 1 << 30;
const double eps = 1e-8;


inline double dot(const P a, const  P b){//A dot B
	return a.real()*b.real() + a.imag()*b.imag();
}

inline double cross(const P a, const P b){//A cross B
	return a.real()*b.imag() - a.imag()*b.real();
}

bool less_P(const P& l, const P& r){
	if (l.real() == r.real())
		return l.imag() < r.imag();
	else return l.real() < r.real();
}

inline void convex_hull(Poly p, Poly& res){
	int k = 0, t;
	res.resize(2 * p.size());
	sort(all(p),less_P);
	reT(i, 0, (int)p.size()){
		while (k > 1 && (cross(res[k - 1] - res[k - 2], p[i] - res[k - 1])<eps))k--;
		res[k++] = p[i];
	}
	t = k;
	rev(i, 0, (int)p.size() - 1){
		while (k > t && (cross(res[k - 1] - res[k - 2], p[i] - res[k - 1])<eps))k--;
		res[k++] = p[i];
	}
	res.resize(k-1);
}





int main(void){
	int n;
	double x, y;
	Poly p, q;
	stringstream ss;string str, token;istringstream is;
	while (true){
		inpur_line(str, is);
		input_token(ss, is, token, n);
		if (n == 0)break;
		p.resize(n);
		rT(i, n){
			inpur_line(str, is);
			input_token(ss, is, token, x);
			input_token(ss, is, token, y);
			p[i].real(x);
			p[i].imag(y);
		}
		convex_hull(p, q);
		cout << n - q.size() << endl;
	}

	return(0);
}