Ruby is playing with the board from a board game.

The board consists of square cells of unit dimensions on a plane, with the topmost left tile defined as . Originally, all of these cells are colored black. Ruby will execute commands of the form , , , , in which she'll flip the colors of the cells contained by a rectangle whose top-left vertex is located at . That is, a cell colored black will become white, and a cell colored white will become black.

At the end of all her flip commands, she wants to know the area covered by white tiles on the board.

#### Constraints

##### Subtask 1 [10%]

##### Subtask 2 [30%]

##### Subtask 3 [60%]

#### Input Specification

The first line of input will contain 2 space-separated integers and . The next lines will each contain a flip command in the form of 4 space-separated integers , , , .

#### Output Specification

On one line, the integer number of cells that are colored white at the end of Ruby's game.

#### Sample Input 1

```
10 2
0 0 10 10
2 2 6 6
```

#### Sample Output 1

`64`

#### Explanation

The board after the 2 commands is shown below.

#### Sample Input 2

```
10 15
0 5 10 5
0 0 1 1
6 5 2 1
3 6 1 1
3 5 1 1
7 2 2 1
4 2 1 1
3 3 1 2
0 8 1 2
6 9 2 1
8 2 1 1
1 2 2 1
1 3 2 2
3 3 2 2
6 2 1 1
```

#### Sample Output 2

`54`

#### Explanation

The board after all 15 commands is shown below.

## Comments

Why is pypy or python's time limit not 4 seconds, but java's is?

Python didn't exist when this problem was authored.

The programming language Python was conceived in the late 1980s, and its implementation was started in December 1989 by Guido van Rossum...

Source: Wikipedia

This problem was written in 2015.

Wikipedia isn't a trusted source

His point is that Python was invented before this question was written.

For the second example, there is only one command with y=0 that flips a single square in the first row, but the first row on the board is quite complex, how is this possible?

y is the column number, not the row number

Happy birthday T-man.

Thanks!