#include <iostream>

 #include<cstdio>

 #include<cstring>

 #include<algorithm>

 #include<stdlib.h>

 #include<vector>

 #include<cmath>

 #include<queue>

 #include<set>

 using namespace std;

 #define N 100000

 #define LL long long

 #define INF 0xfffffff

 const double eps = 1e-;

 const double pi = acos(-1.0);

 const double inf = ~0u>>;

 int main()

 {

     int a,b,c,d,e,f;

     while(scanf("%d%d%d%d%d%d",&a,&b,&c,&f,&e,&d)!=EOF)

     {

         a*=a,b*=b,c*=c,d*=d,e*=e,f*=f;

         double v=sqrt(1.0*a*d*(b+c+e+f-a-d)+1.0*b*e*(a+c+d+f-b-e)

                       +1.0*c*f*(a+b+d+e-c-f)-1.0*a*b*f-1.0*b*c*d-1.0*c*a*e-1.0*d*e*f)/;

             printf("%.4f\n",v);

     }

     return ;

 }