#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define R cin>>
#define ln cout<<'\n'
#define ll long long
#define in(a) insert(a)
#define pb(a) push_back(a)
#define pd(a) printf("%.12f\n",a)
#define mem(a) memset(a,0,sizeof(a))
#define all(c) (c).begin(),(c).end()
#define iter(c) __typeof((c).begin())
#define rrep(i,n) for(ll i=(ll)(n)-1;i>=0;i--)
#define REP(i,m,n) for(ll i=(ll)(m);i<(ll)(n);i++)
#define rep(i,n) REP(i,0,n)
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
ll check(ll n,ll m,ll x,ll y){return x>=0&&x<n&&y>=0&&y<m;}void pr(){ln;}
template<class A,class...B>void pr(const A &a,const B&...b){cout<<a<<(sizeof...(b)?" ":"");pr(b...);}
template<class A>void PR(A a,ll n){rep(i,n)cout<<(i?" ":"")<<a[i];ln;}
const ll MAX=1e9+7,MAXL=1LL<<61,dx[8]={-1,0,1,0,-1,-1,1,1},dy[8]={0,1,0,-1,-1,1,1,-1};
typedef complex<double> P;

double cross(const P& a, const P& b) {return imag(conj(a)*b);}
double area(vector<P> p) {
  double a=0;
  for(int i=0;i<(int)p.size();i++)a+=cross(p[i],p[(i+1)%p.size()]);
  return fabs(a)/2;
}

P C(P a,ll k) {
  if(k==0) a=P(a.real()-1,a.imag());
  else if(k==1) a=P(a.real()+1,a.imag());
  else if(k==2) a=P(a.real(),a.imag()-1);
  else a=P(a.real(),a.imag()+1);
  return a;
}

void Main() {
  vector<P> a(3);
  rep(i,3) {
    double x,y;
    cin >> x >> y;
    a[i]=P(x,y);
  }
  double M=0;
  rep(i,4) {
    rep(j,4) {
      rep(k,4) {
        vector<P> b=a;
        b[0]=C(b[0],i);
        b[1]=C(b[1],j);
        b[2]=C(b[2],k);
        M=max(M,area(b));
      }
    }
  }
  pd(M);
}

int main(){ios::sync_with_stdio(0);cin.tie(0);Main();return 0;}