Competitions

# Data Structures contest

# Pairs

Array of unique integers and a target value **k** are given. Determine the number of pairs of array elements that have a difference equal to a target value **k**.

#### Input

First line contains integers **n** (**2** ≤ **n** ≤ `10`

) and ^{5}**k** (**0** < **k** < `10`

). Second line contains ^{9}**n** unique integers in the range from **0** to `2`

- ^{31}**1**.

#### Output

Print the number of pairs of array integers with difference **k**.

#### Explanation

In the sample there are two pairs of numbers with difference **3**: (**5**, **2**) and (**10**, **7**).

Input example #1

6 3 7 3 5 1 10 2

Output example #1

2