#include <stdio.h> #include <math.h> int main() { double x1,x2,y1,y2,x3,y3; double a,b,c,p; scanf("%lf %lf %lf %lf %lf %lf",&x1,&y1,&x2,&y2,&x3,&y3); a=sqrt((x1-x2)(x1-x2)+(y1-y2)(y1-y2)); b=sqrt((x1-x3)(x1-x3)+(y1-y3)(y1-y3)); c=sqrt((x2-x3)(x2-x3)+(y2-y3)(y2-y3)); p=1.0/2.0*(a+b+c); printf("%.2lf\n",sqrt(p*(p-a)(p-b)(p-c))); return 0; }