**Time limit:**1.00 s**Memory limit:**512 MB

**Input**

The first input line has an integer $n$: the number of rectangles.

After that, there are $n$ lines describing the rectangles. Each line has four integers $x_1$, $y_1$, $x_2$ and $y_2$: a rectangle begins at point $(x_1,y_1)$ and ends at point $(x_2,y_2)$.

**Output**

Print the total area covered by the rectangles.

**Constraints**

- $1 \le n \le 10^5$

- $-10^6 \le x_1 < x_2 \le 10^6$

- $-10^6 \le y_1 < y_2 \le 10^6$

**Example**

Input:

`3`

1 3 4 5

3 1 7 4

5 3 8 6

Output:

`24`