C - problem z dynamiczną obsługą pamięci heap

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

struct Point
{
	float x, y;
};
typedef struct
{	
	float l;
	struct Point A;
	struct Point B;
} line;

int main()
{
	int i=0, n=0;
	float buf=0;
	line *ptr1, *ptr2;

	printf("How many points do you need? ");
	scanf("%d", &n);

	ptr2 = (line*) malloc(sizeof(line)*n);

	while(i!=n)
	{
		ptr1 = (ptr2+i*sizeof(line));

		printf("Give me x coordinate for %i point A: ", i+1);
		scanf("%f", &buf);
		ptr1 -> A.x = buf;
		printf("Give me y coordinate for %i point A: ", i+1);
		scanf("%f", &buf);
		ptr1 -> A.y = buf;
		printf("\nGive me x coordinate for %i point B: ", i+1);
		scanf("%f", &buf);
		ptr1 -> B.x = buf;
		printf("Give me y coordinate for %i point B: ", i+1);
		scanf("%f", &buf);
		ptr1 -> B.y = buf;
		
		++i;		
		printf("\n");
	}

	i=0;
	while(i!=n) {
		ptr1 = (ptr2+i*sizeof(line));
		printf ("Line no. %d: A=(%f, %f), B=(%f, %f)\n", i+1, ptr1->A.x, ptr1->A.y, ptr1->B.x, ptr1->B.y);
		++i;
	}
	printf("\n");

	free(ptr2);
	
	system("PAUSE");
	return 0;
}