#[allow(unused_imports)] use std::cmp::*; #[allow(unused_imports)] use std::collections::*; // 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")); } const MOD: i64 = 998_244_353; fn main() { // In order to avoid potential stack overflow, spawn a new thread. let stack_size = 104_857_600; // 100 MB let thd = std::thread::Builder::new().stack_size(stack_size); thd.spawn(|| solve()).unwrap().join().unwrap(); } fn solve() { input! { n: usize, p: [usize; n], } let mut inv = vec![0; n]; for i in 0..n { inv[p[i]] = i; } let mut l = inv[0]; let mut r = inv[0]; let mut tot = 1; for i in 1..n { let old = (l, r); l = min(l, inv[i]); r = max(r, inv[i]); if old != (l, r) { continue; } let t = (r + 1 - l) - (i - 1); tot = tot * t as i64 % MOD; } println!("{}", tot); }