#include <iostream>
#include <vector>
#include <string>
#include <iomanip>
#include <queue>
#include <cmath>
#include <algorithm>
#include <tuple>
#include <iomanip>
#include <stdio.h>
#include <numeric>
#include <map>
#include <math.h>

#define int long long
#define double double
#define ull unsigned long long
#define all(a) a.begin(), a.end()
#define pii pair<int, int>
#define pb push_back

using namespace std;

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cout << fixed << setprecision(1);
    vector<pair<int, int>> a(3);
    for (int i = 0; i < 3; i++) {
        cin >> a[i].first >> a[i].second;
    }
    sort(all(a));
//    for (int i = 0 ; i < 3; i++) {
//        cout << a[i].first << " " << a[i].second << "\n";
//    }
    int ans = (a[2].first - a[1].first) * (a[2].second - a[1].second) + (a[2].first - a[0].first) * (a[2].second - a[0].second);
    if (ans < 0) {
        ans = -ans;
    }
    cout << ans / 2;
    if (ans % 2) {
        cout << ".5";
    }
}