Given an array $A$ of $n$ distinct integers in ascending order.
Find the number of pairs $i < j$ such that $A_i + A_j = x$.
### Input
- The first line contains an integer $n$.
- The second line contains $n$ integers $A_i$.
### Output
- Print the number of pairs $(i, j)$.
### Constraints
- $1 \le n \le 10^5$.
- $1 \le A_i, x \le 10^9$.
### Example
Input:
```
5 6
1 2 3 4 5
```
Output:
```
2
```
