Count Unique Pairs with Given Difference

You are given an array of integers and an integer ( k ). Your task is to determine the number of unique pairs ( (a, b) ) such that ( b - a = k ).

If ( k > 0 ), a pair ( (a, b) ) is counted only once even if multiple occurrences exist. For ( k = 0 ), count each distinct number that appears at least twice (each such number contributes exactly one pair). For ( k < 0 ), the answer is defined to be 0.

Please read the input from standard input (stdin) and output the result to standard output (stdout).

inputFormat

The first line of input contains two integers ( n ) and ( k ), where ( n ) is the number of elements in the array and ( k ) is the difference.

The second line contains ( n ) space-separated integers representing the array.

outputFormat

Output a single integer representing the number of unique pairs that satisfy the condition.## sample

7 2
1 7 5 9 2 12 3

4