You have a robot located at point $(0, 0)$ on a 2D plane. The robot can run $n$ command.
If the robot are now at $(x, y)$, and you execute the $i^{th}$ command, your robot will move to $(x + x_i, y + y_i)$.
Each command can only be executed only once. Count the number of way to reach point $(a, b)$.
### Input
- The first line contains an integer $n$.
- The second line contains 2 integers $a, b$.
- The next $n$ lines, each line contains 2 integers $x_i, y_i$.
### Output
- Print the number of ways to reach point $(a, b)$.
### Constraints
- $1 \le n \le 40$.
- $-10^9 \le x_i, y_i, a, b \le 10^9$.
### Example
Input:
```
2
1 1
0 1
1 0
```
Output:
```
1
```