Area covered by squares

$N$ squares lie in the plane. Each square is given by the coordinates of its center and the coordinates of one of its vertices. Rotating the given vertex around the center by $90$, $180$ and $270$ degrees produces the other three vertices, so the two points determine one square.

Write a program that computes the area of the region covered by at least one square. A part where several squares overlap counts once.

The first line holds the integer $N$, the number of squares. ($0 < N < 10$)

Each of the next $N$ lines holds four integers separated by spaces and describes one square. The first two are the $x$ and $y$ coordinates of the center, the last two are the $x$ and $y$ coordinates of one vertex.

All coordinates are integers in the range $[-50, 50]$, and the vertex differs from the center.

Print one line holding the area covered by the squares, rounded to the nearest integer. If the fractional part of the area is exactly $0.5$, round up.