Given an array of integers and a target value, determine the number of pairs of array elements that have a difference equal to the target value.

Example

$k=1$

$arr=[1,2,3,4]$

There are three values that differ by $k=1$: $2-1=2$, $3-2=1$, and $4-3=1$. Return $3$.

Function Description

Complete the pairs function below.

pairs has the following parameter(s):

int k: an integer, the target difference
int arr[n]: an array of integers

Returns

int: the number of pairs that satisfy the criterion

Input Format

The first line contains two space-separated integers $n$ and $k$, the size of $arr$ and the target value.

The second line contains $n$ space-separated integers of the array $arr$.

Constraints

$2 \leq n \leq 10^5$
$0 < k < 10^9$
$0<arr[i]<2^{31}-1$
each integer $\boldsymbol{arr}[i]$ will be unique

Sample Input
STDIN Function
----- --------
5 2 arr[] size n = 5, k =2
1 5 3 4 2 arr = [1, 5, 3, 4, 2]

Sample Output
3

Explanation

There are 3 pairs of integers in the set with a difference of 2: [5,3], [4,2] and [3,1]. .

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