#include <stdio.h>
typedef struct {int x; int y;} point;
point verts[] = {{0, 0}, {0, 1}, {1, 0}};
point vertt[] = {{2, 2}, {2, 3}, {3, 2}};
int main(){
void at(point * pol, point p1){
void tz(point p2, point p3){if(!((
p2.x*p3.y - p3.x*p2.y + p3.x*p1.y - p1.x*p3.y + p1.x*p2.y - p2.x*p1.y
)&7)) printf("zero for %d %d, %d %d, %d %d\n",
  p1.x, p1.y, p2.x, p2.y, p3.x, p3.y);}
tz(pol[0], pol[1]); tz(pol[1], pol[2]); tz(pol[2], pol[0]);}
{int k=3; while(k--) {at(verts, vertt[k]); at(vertt, verts[k]);}}
return 0;
}