#![allow(unused_imports)] #![allow(non_snake_case)] use std::collections::HashMap; use std::collections::HashSet; use std::collections::VecDeque; #[allow(unused_macros)] macro_rules! read { ([$t:ty] ; $n:expr) => ((0..$n).map(|_| read!([$t])).collect::>()); ($($t:ty),+ ; $n:expr) => ((0..$n).map(|_| read!($($t),+)).collect::>()); ([$t:ty]) => (rl().split_whitespace().map(|w| w.parse().unwrap()).collect::>()); ($t:ty) => (rl().parse::<$t>().unwrap()); ($($t:ty),*) => {{ let buf = rl(); let mut w = buf.split_whitespace(); ($(w.next().unwrap().parse::<$t>().unwrap()),*) }}; } #[allow(dead_code)] fn rl() -> String { let mut buf = String::new(); std::io::stdin().read_line(&mut buf).unwrap(); buf.trim_end().to_owned() } fn main() { let (_, x) = read!(usize, usize); let a = read!([usize]); let mut v = vec![0u32; 100000 + 1]; let mut ans = 0u64; for e in &a { if *e > x { continue; } else { if x == *e << 1{ ans += 1; } if (x - *e) <= 100000 + 1 { ans += v[x - *e] as u64 * 2; v[*e] += 1; } } } println!("{}", ans); }