use std::collections::HashMap;

fn main() {
    let mut xx = String::new();
    std::io::Read::read_to_string(&mut std::io::stdin(), &mut xx).ok();
    let xx: Vec<i64> = xx.split_whitespace().flat_map(str::parse).collect();

    let mut count = HashMap::new();
    for &x in &xx[2..] {
        *count.entry(x).or_insert(0) += 1;
    }

    let mut answer = 0;
    for &x in &xx[2..] {
        answer += count.get(&(xx[1] - x)).unwrap_or(&0);
    }

    println!("{answer}");
}