#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <cassert>
#include <iostream>
#include <cctype>
#include <sstream>
#include <string>
#include <list>
#include <vector>
#include <queue>
#include <set>
#include <stack>
#include <map>
#include <utility>
#include <numeric>
#include <algorithm>
#include <iterator>
#include <bitset>
#include <complex>
#include <fstream>
using namespace std;
typedef long long ll;
const double EPS = 1e-9;
const double PI = acos(-1);
typedef vector<int> vint;
typedef pair<int, int> pint;
#define rep(i, n) REP(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define MSG(a) cout << #a << " " << a << endl;
#define REP(i, x, n) for(int i = x; i < n; i++)
template<class T> T RoundOff(T a){ return int(a+.5-(a<0)); }
template<class T, class C> void chmax(T& a, C b){ if(a < b) a = b; }
template<class T, class C> void chmin(T& a, C b){ if(b < a) a = b; }
template<class T, class C> pair<T, C> mp(T a, C b){ return make_pair(a, b); }

struct P{ double x, y; };
bool operator == (P x, P y)
{   return x.x == y.x && x.y == y.y;    }
bool operator != (P x, P y)
{   return !(x == y);  }
bool operator < (P x, P y)
{ return x.x < y.x || (x.x == y.x && x.y < y.x); }

int main()
{    
    int n;
    while(cin >> n && n)
    {
        vector<P> points(n); char k;
        rep(i, n)
            cin >> points[i].x >> k >> points[i].y;
        
        sort(ALL(points));
        
        int res = 0;
        P s = points[0];
        P begin = s;
        
        double mrad = PI * 3 / 2;
        do
        {
            res++;
            vector<P>::iterator deleted;
            
            double irad = 0;
            for(vector<P>::iterator it = points.begin() + (res == 1); it != points.end(); it++)
            {
                double rad = atan2((*it).y - begin.y, (*it).x - begin.x);
                rad = rad < 0 ? 2 * PI + rad : rad;
                
                rad = rad < mrad ? 2 * PI - mrad + rad : rad - mrad;
                if(it == points.begin() + (res == 1) || irad < rad)
                {
                    deleted = it;
                    irad = rad;
                }
            }
            mrad += irad;
            if(2 * PI <= mrad) mrad -= 2 * PI;
            
            begin = *deleted;
            points.erase(deleted);
        }
        while(begin != s);
        
        cout << n - res << endl;
    }
}