#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
template<typename T>
bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template<typename T>
bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
void solve();
int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  cout << fixed << setprecision(20);
  int t = 1;
  //cin >> t;
  while (t--) {
    solve();
  }
}
int x[3],y[3];
void solve() {
  rep(i,3)cin>>x[i]>>y[i];
  double ans=0.0;
  rep(S,1<<6){
    vector<int>X(x,x+3),Y(y,y+3);
    int s=S;
    rep(i,3){
      int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};
      X[i]+=dx[s%4],Y[i]+=dy[s%4];
      s/=4;
    }
    int a=X[1]-X[0],b=Y[1]-Y[0];
    int c=X[2]-X[0],d=Y[2]-Y[0];
    chmax(ans,(double)abs(a*d-b*c)/2.0);
  }
  cout<<ans<<endl;
}