#include <iostream>
#include <vector>
#include <string>
#include <unordered_set>
#include <limits>
#include <cmath>
#include <iomanip>
#include <algorithm>
#include <cassert>

using namespace std;


double dist(double x1, double y1, double x2, double y2){
    return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}

int32_t main() {
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    double x1,y1;
    double x2,y2;
    double x3,y3;
    cin>>x1>>y1>>x2>>y2>>x3>>y3;
    double a = dist(x1,y1, x2, y2);
    double b = dist(x1,y1, x3, y3);
    double c = dist(x2,y2, x3, y3);
    double p = a+b+c;
    int ans = 1e-3 + sqrt(p*(p-a*2)*(p-b*2)*(p-c*2));
    cout<<ans;
}