#include <iostream>
#include <string>
#include <vector>
using namespace std;

int cross(double x1, double y1, double x2, double y2) {
    if (0 < x1 * y2 - y1 * x2) return 1;
    return -1;
}

int main() {
    int n;
    while (cin >> n, n) {
        char c;
        vector<double> x(n), y(n);
        for (int i=0; i<n; ++i) {
            cin >> x[i] >> c >> y[i];
        }
        vector<bool> touch(n, false);
        for (int i=0; i<n; ++i) {
            for (int j=i+1; j<n; ++j) {
                bool ok = true;
                int d = 0;
                for (int k=0; k<n; ++k) {
                    if (k == i || k == j) continue;
                    int dd = cross(x[j] - x[i], y[j] - y[i], x[k] - x[i], y[k] - y[i]);
                    if (d == 0) {
                        d = dd;
                    } else if (d != dd) {
                        ok = false;
                        break;
                    }
                }
                if (ok) {
                    touch[i] = touch[j] = true;
                }
            }
        }
        int cnt = n;
        for (int i=0; i<n; ++i) cnt -= touch[i];
        cout << cnt << endl;
    }
    return 0;
}