Given $n$ rectangles on a two-dimensional coordinate grid. The rectangles have coordinates of the bottom-left corner as $(x_1, y_1)$ and the top-right corner as $(x_2, y_2)$, with their sides parallel to either the x-axis or the y-axis.
### Input
- The first line contains an integer $n$.
- The next $n$ lines each contain four integers $x_1, y_1, x_2, y_2$, representing a rectangle with coordinates of the bottom-left corner as $(x_1, y_1)$ and the top-right corner as $(x_2, y_2)$.
### Output
- Print an integer representing the total area covered by the rectangles.
### Constraints
- $1 \leq n \leq 10^5$.
- $1 \leq x_1, y_1, x_2, y_2 \leq 10^5$.
### Example
Input:
```
3
2 1 6 5
1 4 5 8
4 2 9 7
```
Output:
```
46
```
