P1102 A - B Pairs

出题是一件痛苦的事情！ 相同的题目看多了也会有审美疲劳，于是我舍弃了大家所熟悉的 A+B Problem，改用 A-B 了哈哈！

Given a sequence of positive integers and a positive integer $C$, compute the number of pairs $(A, B)$ such that $A - B = C$. Pairs with the same values at different positions are considered distinct.

The input consists of two lines. The first line contains two positive integers $N, C$. The second line contains $N$ positive integers, which form the sequence to be processed.

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

Constraints: - For $75\%$ of the testdata, $1 \leq N \leq 2000$. - For $100\%$ of the testdata, $1 \leq N \leq 2 \times 10^5$, $0 \leq a_i < 2^{30}$, $1 \leq C < 2^{30}$. Two new testdata sets were added on 2017/4/29. Translated by ChatGPT 5