A-B Pairs

Problem Description

You are given a sequence of numbers and a number $C$. Count the number of pairs $(A, B)$ satisfying $A - B = C$ (two numbers at different positions with the same value are counted as different pairs).

Input Format

Two lines in total.

The first line contains two integers $N$, $C$.

The second line contains $N$ integers, the sequence to process.

Output Format

One line containing the number of pairs in the sequence that satisfy $A - B = C$.

Sample Input

4 1
1 1 2 3

Sample Output

3

Constraints

$1\leq N \leq 2\times 10^5$, $1 \leq C \leq 2\times 10^5$. The $N$ input numbers are guaranteed to be below $2^{30}$.