// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let 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, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}
// ---------- end input macro ----------

fn run() {
    input!(n: usize, m: usize);
    const MOD: usize = 998_244_353;
    let mut map = std::collections::BTreeMap::new();
    let mut f = |s: usize, e: usize| -> usize {
        if s > e {
            return 0;
        }
        if let Some(p) = map.get(&(s, e)) {
            return *p;
        }
        type Mat = (usize, usize, usize);
        let mut mat = (e - s + 1, (e + s) * (e - s + 1) / 2 % MOD, e - s + 1);
        let mut t = (1, 0, 1);
        let mul = |a: &Mat, b: &Mat| -> Mat {
            (a.0 * b.0 % MOD, (a.0 * b.1 + a.1 * b.2) % MOD, a.2 * b.2 % MOD)
        };
        let mut n = n;
        while n > 0 {
            if n & 1 == 1 {
                t = mul(&t, &mat);
            }
            mat = mul(&mat, &mat);
            n >>= 1;
        }
        let res = t.1;
        map.insert((s, e), res);
        res
    };
    let mut ans = 0;
    for i in 1..=m {
        let x = MOD + f(1, i) - f(1, i - 1);
        let y = MOD + f(i, m) - f(i + 1, m);
        ans += i * (2 * MOD + x - y) % MOD;
    }
    ans %= MOD;
    println!("{}", ans);
}

fn main() {
    run();
}