#include<bits/stdc++.h>
using namespace std;

double distance(double x,double y,double z,double a)
{
    return sqrt((x - y) * (x - y) + (z - a) * (z - a));
}

int main()
{
    double x1,y_1,x2,y2,x3,y3,dis1,dis2,dis3,square;
    cin >> x1 >> y_1 >> x2 >> y2 >> x3 >> x3;
    dis1 = distance(x1, y_1, x2, y2);
    dis2 = distance(x2, y2, x3, y3);
    dis3 = distance(x1, y_1, x3, y3);
    square = (dis1 + dis2 + dis3) / 2 * 1.0;
    printf("%.2lf\n", round(sqrt(square * (square - dis1) * (square - dis2) * (square - dis3))));
}