//proconio macro_rules! input { (source = $s:expr, $($r:tt)*) => { let mut iter = $s.split_whitespace(); input_inner!{iter, $($r)*} }; ($($r:tt)*) => { let mut s = { use std::io::Read; let mut s = String::new(); std::io::stdin().read_to_string(&mut s).unwrap(); s }; let mut iter = s.split_whitespace(); input_inner!{iter, $($r)*} }; } macro_rules! input_inner { ($iter:expr) => {}; ($iter:expr, ) => {}; ($iter:expr, $var:ident : $t:tt $($r:tt)*) => { let $var = read_value!($iter, $t); input_inner!{$iter $($r)*} }; } macro_rules! read_value { ($iter:expr, ( $($t:tt),* )) => { ( $(read_value!($iter, $t)),* ) }; ($iter:expr, [ $t:tt ; $len:expr ]) => { (0..$len).map(|_| read_value!($iter, $t)).collect::>() }; ($iter:expr, chars) => { read_value!($iter, String).chars().collect::>() }; ($iter:expr, usize1) => { read_value!($iter, usize) - 1 }; ($iter:expr, $t:ty) => { $iter.next().unwrap().parse::<$t>().expect("Parse error") }; } fn main() { input!{ n:usize,m:i64,a:[i64;n], } let mut ans:i64=0; let mut flag1:bool = true; let mut flag2:bool = true; let mut memo: std::collections::HashMap = std::collections::HashMap::new(); for t in &a{ if t%m==0{ if flag1 { ans+=1; flag1=false; } continue; } if t%m*2==m{ if flag2{ ans+=1; } flag2=false; continue; } *memo.entry(t%m).or_default()+=1_i64; } dbg!(&ans); for (&key,&val) in memo.iter(){ let mut rem = m-key; if rem==key{ ans+=val; continue; } if memo.get(&rem) != None { let mut vval = *memo.get(&rem).unwrap(); if val>vval{ ans+=val; } else if val == vval{ if key