#include <bits/stdc++.h>
using namespace std;
int main(){
    double x11,y11,x2,y2,x3,y3,a,b,c,p,ans;
    cin>>x11>>y11>>x2>>y2>>x3>>y3;
    a=sqrt((x11-x2)*(x11-x2)+(y11-y2)*(y11-y2));
    b=sqrt((x11-x3)*(x11-x3)+(y11-y3)*(y11-y3));
    c=sqrt((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3));
    p=0.5*(a+b+c);
    ans=sqrt(p*(p-a)*(p-b)*(p-c));
    printf("%.2lf",ans);
    return 0;
}