# UKSPC Practice Problems » Counting Squares

Your input is a series of rectangles, one per line. Each rectangle is specified as two points (X, Y) that specify the opposite corners of a rectangle. All coordinates will be integers in the range 0 to 100. For example, the line

`5 8 7 10`

specifies the rectangle whose corners are (5,8), (7,8), (7,10), and (5,10).

If drawn on graph paper, that rectangle would cover four squares. Your job is to count the number of unit squares that are covered by any one of the rectangles given as input. Any square covered by more than one rectangle should only be counted once.

## Input Format

The input format is a series of lines, each containing 4 integers. Four -1's are used to separate problems, and four -2's are used to end the last problem. Otherwise, the numbers are the x, y coordinates of two points that are opposite corners of a rectangle.

## Output Format

Your output should be the number of squares covered by each set of rectangles. Each number should be printed on a separate line.

## Sample Input

```5 8 7 10
6 9 7 8
6 8 8 11
-1 -1 -1 -1
0 0 100 100
50 75 12 90
39 42 57 73
-2 -2 -2 -2
```

```8
10000```