#![allow(unused_imports)]
use std::cmp::*;
use std::collections::*;
use std::io::Write;
use std::ops::Bound::*;

#[allow(unused_macros)]
macro_rules! debug {
    ($($e:expr),*) => {
        #[cfg(debug_assertions)]
        $({
            let (e, mut err) = (stringify!($e), std::io::stderr());
            writeln!(err, "{} = {:?}", e, $e).unwrap()
        })*
    };
}

fn main() {
    let v = read_vec::<i64>();
    let (n, m) = (v[0], v[1]);
    let a = read_vec::<i64>();

    let mut a_count = HashMap::new();
    for aa in a {
        *a_count.entry(aa % m).or_insert(0) += 1;
    }

    let mut ans = 0;
    ans += min(2, 2 * *a_count.get(&0).unwrap_or(&0));

    for (&k, &v) in &a_count {
        if k == 0 {
            continue;
        }
        if let Some(&x) = a_count.get(&(m - k)) {
            if x == m - k {
                ans += 2 * v;
            } else {
                ans += max(v, x);
            }
        } else {
            ans += 2 * v;
        }
    }
    ans /= 2;

    println!("{}", ans);
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}