#include <stdio.h>
#include <math.h>
double abs(double a){if(a<0)return -a;return a;}
int main(){double a,b,c,d,e,f,g;
    while(scanf("%lf %lf %lf %lf %lf %lf",&a,&b,&c,&d,&e,&f)!=EOF)
        printf("%.2lf\n",3.141592653589793
            *sqrt((a-e)*(a-e)+(b-f)*(b-f))
            *sqrt((a-c)*(a-c)+(b-d)*(b-d))
            *sqrt((c-e)*(c-e)+(d-f)*(d-f))
            /abs((a-c)*(b-f)-(a-e)*(b-d)));
    return 0;
}

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