#include <bits/stdc++.h>
using namespace std;
const vector<int> dx = {0, 0, 1, -1};
const vector<int> dy = {1, -1, 0, 0};
#define vec vector
#define int long long
#define double long double
#define ll long long
#define pii pair<int,int>
#define pq priority_queue
#define all(V) begin(V),end(V)
#define tple tuple<int,int,int>
template<class T, class U> inline bool chmax(T &a, const U &b) { if (a < b) { a = b; return true; } return false; }
template<class T, class U> inline bool chmin(T &a, const U &b) { if (a > b) { a = b; return true; } return false; }
#define nexper(Z) next_permutation(all(Z))
#define pb push_back
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define req(i, x, n) for (int i = x; i < (int)(n); i++)
#define rex(i, n) for (int i = 1; i <= (int)(n); i++)
#define rey(i, x, n) for (int i = x; i <= (int)(n); i++)
#define cleout(i) cout << fixed << setprecision(i)
struct Point {long long x, y;};
Point operator+(const Point& a1, const Point& a2) {return Point{ a1.x + a2.x, a1.y + a2.y };}
Point operator-(const Point& a1, const Point& a2) {return Point{ a1.x - a2.x, a1.y - a2.y };}
bool operator<(const Point& a1, const Point& a2) {if (a1.x < a2.x) return true;if (a1.x > a2.x) return false;if (a1.y < a2.y) return true;return false;}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int a,b,c,d,e,f;
    cin>>a>>b>>c>>d>>e>>f;
    double ans=0;
    rep(i,4){
        rep(j,4){
            rep(k,4){
                int na=a+dx[i];
                int nb=b+dy[i];
                int nc=c+dx[j];
                int nd=d+dy[j];
                int ne=e+dx[k];
                int nf=f+dy[k];
                int aa=na;
                int bb=nb;
                na-=aa;nb-=bb;
                nc-=aa;nd-=bb;
                ne-=aa;nf-=bb;
                chmax(ans,abs(nc*nf-nd*ne)/2.0);
            }
        }
    }
    cleout(10)<<ans;
    return 0;

}