Given a rectangle in the 2D space with four coordinates are (a, c), (b, c), (a, d) and (b, d), compute its area.
Note that b may be greater or less than a, and the same as d and c.
You may use abs function as an assistant to solve this problem (by including <stdlib.h>)
Four integers are given as input: a, b, c, and d, in that order.
Positive integer rectangle area.
Ensure that the output, including formatting, exactly matches the provided samples.