Consider a square chessboard with cells and queens on the chessboard (Note: there are no other chess pieces besides the queens).

A queen can move vertically, horizontally or diagonally. As an example, consider the square chessboard with cells with one queen (denoted by the `♕`

notation) in Figure 1 below. The cells that can be reached by the queen are marked with the `◯`

notation. There are cells that cannot be reached by the queen.

Your task is to calculate the number of cells that are **NOT** reachable by any queens.

#### Input Specification

The first line contains two integers, and . Following are lines. Each line contains two integers and , representing the location of a queen, i.e., the queen is at th row and th column .

#### Output Specification

The number of cells that are not reachable by any queens.

#### Sample Input 1

```
6 1
4 3
```

#### Output for Sample Input 1

`16`

#### Sample Input 2

```
6 2
4 3
6 4
```

#### Output for Sample Input 2

`9`

#### Explanation

Figure 1 and Figure 2 correspond to Sample 1 and Sample 2, respectively.

## Comments