#include <iostream>
#include <cmath>
using namespace std;
int x1,y_1,x2,y2,x3,y3;
int main(){
    cin>>x1>>y_1>>x2>>y2>>x3>>y3;
    double a=sqrt(pow(x1-x2,2)+pow(y_1-y2,2));
    double b=sqrt(pow(x1-x3,2)+pow(y_1-y3,2));
    double c=sqrt(pow(x2-y2,2)+pow(x3-y3,2));
    double s=0.5*(a+b+c);
    cout<<(int)round(sqrt(s*(s-a)*(s-b)*(s-c)));
    return 0;
}