#include <iostream>
#include <cstdio>
using namespace std;

int main() {
	double x[3] = { .0 }, y[3] = { .0 }, sum = .0, z, a, b ,c;
	char t;

	cin >> x[0] >> t >> y[0] >> x[1] >> t >> y[1];
	while (cin >> x[2]) {
		cin >> t >> y[2];
		sum += ((x[2] - x[0]) * (y[1] - y[0]) - (x[1] - x[0]) * (y[2] - y[0])) / 2;
		x[1] = x[2], y[1] = y[2];
		cout << sum << endl;
	}
	printf("%.6lf\n", sum);
	return 0;
}