#include <stdio.h>

int f();

typedef struct {
	int x, y;
} Point;

int main()
{
	int res = f(&(Point) { .x = 3, .y =  8 },
	            &(Point) { .x = 3, .y = -1 });
	printf("%d\n", res);
	return 0;
}

int f(Point* lhs, Point* rhs)
{
	return lhs->x * rhs->y - lhs->y * rhs->x;
}