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?

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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.

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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!