#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <queue>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <memory.h>
#include <ctime>
#include <bitset>
#include <unordered_map>
#include <unordered_set>

using namespace std;

#define ABS(a) ((a>0)?a:-(a))
#define MIN(a,b) ((a<b)?(a):(b))
#define MAX(a,b) ((a<b)?(b):(a))
#define FOR(i,a,n) for (int i=(a);i<(n);++i)
#define FI(i,n) for (int i=0; i<(n); ++i)
#define pnt pair <int, int>
#define mp make_pair
#define PI 3.1415926535897
#define MEMS(a,b) memset(a,b,sizeof(a))
#define LL long long
#define U unsigned

double getS(double x1, double y1, double x2, double y2, double x3, double y3)
{
    double X1 = x2 - x1;
    double Y1 = y2 - y1;
    double X2 = x3 - x1;
    double Y2 = y3 - y1;
    return ABS(X1*Y2 - X2*Y1);
}

double x[3];
double y[3];

int main()
{
#ifdef Fcdkbear
    freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);
    double beg = clock();
#else
    freopen("area1.in", "r", stdin);
    freopen("area1.out", "w", stdout);
    double beg = clock();
#endif

    FOR(i, 0, 3)
        cin >> x[i] >> y[i];
    printf("%.15f\n",getS(x[0], y[0], x[1], y[1], x[2], y[2]) / 2.0);

#ifdef Fcdkbear
    double end = clock();
    fprintf(stderr, "*** Total time = %.3lf ***\n", (end - beg) / CLOCKS_PER_SEC);
#endif
    return 0;
}