include <bits/stdc++.h>

using namespace std; int a[5][5];

int main() {

for (int i = 1; i <= 3; i++)
	cin >> a[i][1] >> a[i][2];
double f, b, c;
f = sqrt(pow(a[1][1] - a[2][1], 2) + pow(a[1][2] - a[2][2], 2));
b = sqrt(pow(a[1][1] - a[3][1], 2) + pow(a[1][2] - a[3][2], 2));
c = sqrt(pow(a[2][1] - a[3][1], 2) + pow(a[2][2] - a[3][2], 2));
double d = (f + b + c) / 2;
double s = sqrt(d * (d - f) * (d - b) * (d - c));
printf("%.2lf", s);
return 0;

}