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**

There are three values that differ by : , , and . Return .

**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 and , the size of and the target value.

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

**Constraints**

- each integer 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]. .