#include <cmath>

#include <cstdio>

#include <cstring>

#include <iostream>

#include <algorithm>

using namespace std;

#define INF (1e9)

#define eps (1e-4)

#define pi (3.1415926535)

struct point

{

    double x,y;

};

struct point ai[];

struct line {

    double k,b;

    line *another;

    void updata(struct point a,struct point bb)

    {

        another=new line;

        if(a.x==bb.x) k=INF,b=a.x;

        else

        {

            if(a.y==bb.y) k=,b=a.y;

            else

            {

                k=(bb.y-a.y)/(bb.x-a.x);

                b=a.y-k*a.x;

            }

        }

        if(k==)

        {

            another->k=INF,another->b=(a.x+bb.x)/2.0;

        }

        else if(k==INF)

        {

            another->k=,another->b=(a.y+bb.y)/2.0;

        }

        else

        {

            another->k=-1.0/k;

            struct point temp;

            temp.x=(a.x+bb.x)/2.0;

            temp.y=(a.y+bb.y)/2.0;

            another->b=temp.y-another->k*temp.x;

        }

    }

};

struct line bi[],ci[];

struct point getnode(line a,line b)

{

    struct point res;

    res.x=(b.b-a.b)/(a.k-b.k);

    res.y=a.k*res.x+a.b;

    return res;

}

double dist(struct point a,struct point b)

{

    double aa=(a.x-b.x)*(a.x-b.x);

    double bb=(a.y-b.y)*(a.y-b.y);

    aa=sqrt(aa+bb);

    return aa;

}

double fgcd(double x, double y) {

    while (fabs(x)>eps&&fabs(y)>eps)

    {

        if (x > y) x-=floor(x/y)*y;

        else y-=floor(y/x)*x;

    }

    return x + y;

}

int main()

{

    for(int i=;i<=;i++) cin>>ai[i].x>>ai[i].y;

    bi[].updata(ai[],ai[]);

    bi[].updata(ai[],ai[]);

    bi[].updata(ai[],ai[]);

    for(int i=;i<=;i++) ci[i]=*bi[i].another;

    struct point o=getnode(ci[],ci[]);

    double R=dist(o,ai[]);

    double vi[];

    vi[]=dist(ai[],ai[]);

    vi[]=dist(ai[],ai[]);

    vi[]=dist(ai[],ai[]);

    sort(vi+,vi+);

    double an[];

    an[]=2.0*asin(vi[]/(2.0*R));

    an[]=2.0*asin(vi[]/(2.0*R));

    an[]=2.0*pi-an[]-an[];

    sort(an+,an+);

    double ans1=fgcd(an[],an[]);

    double ans2=fgcd(an[],an[]);

    double ans=fgcd(max(ans1,ans2),min(ans1,ans2));

    double ans_=(2.0*pi-ans)/2.0;

    printf("%.9lf",R*R*sin(ans)*pi/ans);

    return ;

}