#include "stdio.h"
#include "string.h"
#include "stdlib.h"
#include "math.h"
#include "iostream"
#include "ctime"
using namespace std;
typedef struct node{
    double x, y;
}node;
double Cal_Area(node o, node f1, node f2){
    return fabs((f1.x-o.x)*(f2.y-o.y)-(f1.y-o.y)*(f2.x-o.x))/2.0;
}
int main(){
    node p[3];
    while(scanf("%lf%lf%lf%lf%lf%lf", &p[0].x, &p[0].y, &p[1].x, &p[1].y, &p[2].x, &p[2].y)!=EOF){
        printf("%.2lf\n", Cal_Area(p[0], p[1], p[2]));
    } 
}