Помогите найти ошибку

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>

typedef struct {
int x;
int y;
} Point;

typedef struct {
Point a;
Point b;
Point c;
} Triangle;

typedef struct {
double a;
double b;
double c;
} Box;

double length(Point* a, Point* b) {
return sqrt(pow(a->x - b->x, 2) + pow(a->y - b->y, 2));
}

Box lines(Triangle* t) {
Box box;
box.a = length(&t->a, &t->b);
box.b = length(&t->b, &t->c);
box.c = length(&t->c, &t->a);
return box;
}

double pp(Box* x) {
return (x->a + x->b + x->c) / 2;
}

double param(Box* x) {
double p = pp(x);
return (p - x->a) * (p - x->b) * (p - x->c);
}

_Bool exist(Triangle* t) {
Box x = lines(t);
double p = pp(&x);
return param(&x) > 0;
}

double perimeter(Triangle* t) {
Box x = lines(t);
return x.a + x.b + x.c;
}

double area(Triangle* t) {
Box x = lines(t);
double p = pp(&x);
return sqrt(p * param(&x));
}

Point coord(const char* point) {
Point p;
printf("%sx: ", point);
scanf_s("%i", &p.x);
printf("%sy: ", point);
scanf_s("%i", &p.y);
return p;
}

Triangle coords() {
Triangle t;
t.a = coord("A");
t.b = coord("B");
t.c = coord("C");
return t;
}

int main(void) {
Triangle t = coords();
if (exist(&t)) {
double p = perimeter(&t);
double a = area(&t);
printf("%.1lf %.1lf\n", p, a);
}
system("pause > nul");
return 0;
}

a, b, c не должны быть целыми