#include <iostream>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>	// require sort next_permutation count __gcd reverse etc.
#include <cstdlib>	// require abs exit atof atoi 
#include <cstdio>		// require scanf printf
#include <functional>
#include <numeric>	// require accumulate
#include <cmath>		// require fabs
#include <climits>
#include <limits>
#include <cfloat>
#include <iomanip>	// require setw
#include <sstream>	// require stringstream 
#include <cstring>	// require memset
#include <cctype>		// require tolower, toupper
#include <fstream>	// require freopen
#include <ctime>		// require srand
#include <complex>
#define rep(i,n) for(int i=0;i<(n);i++)
#define ALL(A) A.begin(), A.end()

// 許容する誤差ε
#define EPS (1e-10)
// 2つのスカラーが等しいかどうか
#define EQ(a,b) (abs((a)-(b)) < EPS)
// 2つのベクトルが等しいかどうか
#define EQV(a,b) ( EQ((a).real(), (b).real()) && EQ((a).imag(), (b).imag()) )

using namespace std;

typedef complex<double> P;
typedef pair<double,double> PP;
// 反時計順にソート
bool cmp (P a, P b )
{
	double arga = arg (a );
	double argb = arg (b );
	if (!EQ (arga, argb ) ){
		return arga < argb;
	} // end if

	return abs (a ) > abs (b );
}
/*
bool cmp (P a, P b )
{
	double cosa = a.real()/abs (a );		
	double sina = a.imag()/abs (a );
	double cosb = b.real()/abs (b );
	double sinb = b.imag()/abs (b );
	if (sina >= 0. && sinb >= 0. ){
		return cosa > cosb;
	}else
	if (sina < 0. && sinb < 0. ){
		return cosa < cosb;
	}else
	if (sina >= 0. && sinb < 0. ){
		return sina > sinb;
	}else
	if (sina < 0. && sinb >= 0. ){
		return sina < sinb;
	} // end if

	return abs (a ) > abs (b );
}
*/
// 外積 (cross product) : a×b = |a||b|sinΘ
double cross(P a, P b) {
  return (a.real() * b.imag() - a.imag() * b.real());
}

int main()
{
//	cut here before submit 
//	freopen ("testcase.EPRB", "r", stdin );
	int n;
	while (scanf ("%d", &n ), n ){
		vector<P> p (n );
		rep (i, n ){
			double x, y;
			scanf ("%lf,%lf", &x, &y );
			p[i].real() = x; p[i].imag() = y;
		} // end rep
										
		// 原点回りに反時計回りにソート
		sort (ALL (p ), cmp );
/*
		rep (i, n ){
			cerr << '(' << p[i].real() << ',' << p[i].imag() << ')' << endl;
		} // end rep
*/
		set<PP> convex_hull; convex_hull.clear();
		for (int i = 0; i < n; i++ ){
			for (int j = i+1; j < n; j++ ){
				bool ok = true;
				rep (k, n ){
					if (k == i || k == j ) continue;
					if (cross (p[j] - p[i], p[k] - p[i] ) > 0. ) continue;
					ok = false;
					break;
				} // end rep
				if (ok ){
					convex_hull.insert (PP (p[i].real(), p[i].imag() ) );
					convex_hull.insert (PP (p[j].real(), p[j].imag() ) );
				} // end if
			} // end for
		} // end for
		printf ("%d\n", n - (int)convex_hull.size() );
/*
		set<PP>::iterator it = convex_hull.begin();
		for (; it != convex_hull.end(); it++ ){
			cerr << '(' << (*it).first << ',' << (*it).second << ')' << endl;
		} // end for
*/		
	} // end loop

		
	return 0;
}