#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
    vector<pair<int, int>> x(3);
    rep(i,3) cin >> x[i].first >> x[i].second;
    lb ans = 0;
    auto dfs = [&](auto dfs, int c) -> void {
        if(c==3){
            dbg(x);
            int a = (x[1].first-x[0].first)*(x[2].second-x[0].second)-(x[2].first-x[0].first)*(x[1].second-x[0].second);
            a = abs(a);
            ans = max(ans, (lb)a/2.0);
            return;
        }
        x[c].first+=1;
        dfs(dfs, c+1);
        x[c].first-=2;
        dfs(dfs, c+1);
        x[c].first++;
        x[c].second++;
        dfs(dfs,c+1);
        x[c].second-=2;
        dfs(dfs,c+1);
        x[c].second+=1;
    };
    dfs(dfs,0);
    cout << fixed<<setprecision(16)<< ans << endl;
    return 0;
}