## Problem Description

You will be given a number of rectangles in the plane and asked to determine
the area that they cover. The rectangles may overlap.

## Input

The first line of input will contain a single integer T ≤ 10 giving the number
of test cases to follow. Each test case begins with a line with a single integer
n giving the number of rectangles that will follow. There will be at most 20.
The next n lines will describe the n rectangles. Each of these will consist of
four whitespace separated integers xmin ymin xmax ymax. These coordinates
will will fit within a signed 32-bit integer.

## Output

For each test case, you are to output the total area covered by the squares.

## Sample Input

1
3
0 0 4 10
1 -1 4 1
-2 -2 -1 -1

## Sample Output

44

## Source

2008-2009 North-America North-East Preliminary