# Coordinate Compression - Union of Rectangles

Time Limit : 6 sec, Memory Limit : 262144 KB

# Union of Rectangles

ʏ $N$ ̒܂B e̕ӂ́Ax ܂ y ɕsŁA$i$ ڂ̒̍̍W $(x1_i, y1_i)$, E̍W $(x2_i, y2_i)$ łBPȏ̒ŕĂ镔̖ʐς߂ĂB

## Constraints

• $1 \leq N \leq 2000$
• $|10^9 \leq x1_i < x2_i\leq 10^9$
• $|10^9 \leq y1_i < y2_i\leq 10^9$

## Input

͈͂ȉ̌ŗ^B

$N$
$x1_1$ $y1_1$ $x2_1$ $y2_1$
$x1_2$ $y1_2$ $x2_2$ $y2_2$
:
$x1_N$ $y1_N$ $x2_N$ $y2_N$

## Output

Pȏ̒ŕĂ镔̖ʐς 1 sɏo͂B

## Sample Input 1

2
0 0 3 4
1 2 4 3


## Sample Output 1

13


## Sample Input 2

3
1 1 2 5
2 1 5 2
1 2 2 5


## Sample Output 2

7


## Sample Input 3

4
0 0 3 1
0 0 1 3
0 2 3 3
2 0 3 3


## Sample Output 3

8