#include <iostream>
#include <cstdio>
#include <complex>
#include <cmath>

using namespace std;

typedef complex<double> xy_t;
xy_t P[110];

int main (){
	int N = 0;
	double x, y;
	while (~scanf("%lf,%lf", &x, &y)){
		P[N++] = xy_t(x,y);
	}
	double sum = 0.0;
	for(int i = 0; i < N - 2; i++){
		xy_t a = P[0], b = P[(i+1) % N] , c = P[(i+2) % N];
		cout << a.real() << " " << a.imag() << endl;
		cout << b.real() << " " << b.imag() << endl;
		cout << c.real() << " " << c.imag() << endl;
		cout << endl;		
		sum += ((b.real()-a.real())*(c.imag()-a.imag()) - (b.imag()-a.imag())*(c.real()-a.real()));
	}
	printf("%.6f\n" , abs(sum)/2);
}