#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int X[3],Y[3];
int XS[3],YS[3];

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	FOR(i,3) cin>>X[i]>>Y[i];
	int ma=0;
	int dx[4]={0,0,1,-1};
	int dy[4]={1,-1,0,0};
	FOR(i,4) FOR(j,4) FOR(k,4) {
		XS[0]=X[0]+dx[i];
		YS[0]=Y[0]+dy[i];
		XS[1]=X[1]+dx[j];
		YS[1]=Y[1]+dy[j];
		XS[2]=X[2]+dx[k];
		YS[2]=Y[2]+dy[k];
		XS[1]-=XS[0];
		YS[1]-=YS[0];
		XS[2]-=XS[0];
		YS[2]-=YS[0];
		ma=max(ma,abs(XS[1]*YS[2]-XS[2]*YS[1]));
	}
	_P("%f\n",ma/2.0);
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}