#include <stdio.h>
#include <math.h>
double x1, y11, x2, y2, x3, y3, a, b, c, p;
inline double dis(double x1, double y11, double x2, double y2) {
    return sqrt((x1 - x2) * (x1 - x2) + (y11 - y2) * (y11 - y2));
}
int main(void) {
    scanf("%lf %lf %lf %lf %lf %lf", &x1, &y11, &x2, &y2, &x3, &y3);
    a = dis(x1, y11, x2, y2);
    b = dis(x2, y2, x3, y3);
    c = dis(x3, y3, x1, y11);
    p = (a + b + c) / 2;
    printf("%.2lf\n", sqrt(p * (p - a) * (p - b) * (p - c)));
    return 0;
}