#include <iostream>
#include <sstream>
#include <vector>
#include <list>
#include <string>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>
#include <numeric>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
using namespace std;

const int size = 101;
int n;
double X[size];
double Y[size];
double D[size];
bool used[size];

double getCross( double x1, double y1, double x2, double y2 ) {
    return x1 * y2 - y1 * x2;
}

double getDistance( double x1, double y1, double x2, double y2 ) {
    double X = x2 - x1;
    double Y = y2 - y1;
    return X * X + Y * Y;
}

double getDistance( double x, double y ) {
    return getDistance( 0, 0, x, y );
}

void init() {
    for ( int i = 0; i < size; i++ ) {
        used[i] = false;
    }
}

int solve() {
    init();

    bool first = true;
    int pivot;
    double mind;
    for ( int i = 0; i < n; i++ ) {
        if ( first || D[i] < mind ) {
            pivot = i;
            mind = D[i];
            first = false;
        }
    }

    int cnt = 1;
    used[pivot] = true;

    for ( int k = 0; k < n-1; k++ ) {
        for ( int i = 0; i < n; i++ ) {
            if ( used[i] ) continue;
            bool flag = true;
            for ( int j = 0; j < n; j++ ) {
                if ( i == j ) continue;
                double c = getCross( X[i] - X[pivot], Y[i] - Y[pivot], X[j] - X[pivot], Y[j] - Y[pivot] );
                if ( c < 0.0 ) {
                    flag = false;
                    break;
                }
            }
            if ( flag ) {
                cnt++;
                used[i] = true;
                pivot = i;
                break;
            }
        }
    }
    
    return n - cnt;
}

int main() {
    while ( cin >> n && n ) {
        for ( int i = 0; i < n; i++ ) {
            string line;
            cin >> line;
            replace( line.begin(), line.end(), ',', ' ' );
            istringstream is( line );
            is >> X[i] >> Y[i];
            X[i] += 2000.0;
            Y[i] += 2000.0;
            D[i] = getDistance( X[i], Y[i] );
        }
        cout << solve() << endl;
    }
    return 0;
}