use std::cmp::*; // https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 macro_rules! input { ($($r:tt)*) => { let stdin = std::io::stdin(); let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock())); let mut next = move || -> String{ bytes.by_ref().map(|r|r.unwrap() as char) .skip_while(|c|c.is_whitespace()) .take_while(|c|!c.is_whitespace()) .collect() }; input_inner!{next, $($r)*} }; } macro_rules! input_inner { ($next:expr) => {}; ($next:expr,) => {}; ($next:expr, $var:ident : $t:tt $($r:tt)*) => { let $var = read_value!($next, $t); input_inner!{$next $($r)*} }; } macro_rules! read_value { ($next:expr, [ $t:tt ; $len:expr ]) => { (0..$len).map(|_| read_value!($next, $t)).collect::>() }; ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error")); } fn main() { input! { n: usize, k: usize, x: usize, y: usize, a: [usize; n], } const INF: i32 = 1 << 28; let mut dp = vec![vec![-INF; k]; k]; dp[x % k][y % k] = 0; let mut row = vec![-INF; k]; let mut col = vec![-INF; k]; row[x] = 0; col[y] = 0; for &a in &a { let a = a % k; for b in 0..k { let mut ma = max(row[b], col[b]); let rest = (2 * k - a - b) % k; ma = max(ma, max(dp[rest][b], dp[b][rest]) + 1); dp[a][b] = ma; } for b in 0..k { row[a] = max(row[a], dp[a][b]); col[b] = max(col[b], dp[a][b]); } } let ans = row.iter().max().unwrap(); println!("{}", ans); }