#include <bits/stdc++.h>
using namespace std;
//#include<atcoder/all>
//using namespace atcoder;

typedef long long ll;
typedef pair<ll,ll> pll;
#define rep(i,n) for(ll i=0;i<n;i++)
#define chmin(a,b) a=min(a,b)
#define chmax(a,b) a=max(a,b)
#define all(a) a.begin(),a.end()
const int INF=1001001001;
double calculateArea(double x1,  double x2, double x3, double y1,
double y2,double y3) {
    return abs((x1*(y2-y3) + x2*(y3-y1) + x3*(y1-y2)) / 2.0);
}
int main(){
int x[3],y[3];
rep(i,3){
  cin>>x[i]>>y[i];
}
int dx[]={0,0,1,-1};
int dy[]={1,-1,0,0};
double ans=0;
rep(i,4){
  rep(j,4){
    rep(k,4){
      chmax(ans,calculateArea(x[0]+dx[i],x[1]+dx[j],x[2]+dx[k],
      y[0]+dy[i],y[1]+dy[j],y[2]+dy[k]));

    }
  }
}
cout<<setprecision(10)<<ans<<endl;
}