#include <stdio.h>

struct point{
    double x;
    double y;
};
typedef struct point Point;

void input(Point * pv1);

double calcArea(Point v1, Point v2, Point v3);

int main(){
    Point A, B, C;
    double area;
    input(&A);
    input(&B);
    input(&C);
    area = calcArea(A, B, C);
    printf("Dien tich la %0.2lf\n", area);
    return 0;
}

void input(Point * pv1){
    double x,y,i=0;
    printf("Nhap vao toa do diem : ");
    scanf("%lf",&x);
    scanf("%lf",&y);
    pv1->x=x;
    pv1->y=y;

}

double calcArea(Point v1, Point v2, Point v3){
    return abs(v1.x*v2.y+v2.x*v3.y+v3.x*v1.y-v1.y*v2.x-v2.y*v3.x-v3.y*v1.x)/2;
}