fn getline() -> String {
    let mut ret = String::new();
    std::io::stdin().read_line(&mut ret).unwrap();
    ret
}

// https://yukicoder.me/problems/no/3370 (3.5)
fn main() {
    let s = getline().trim().chars().collect::<Vec<_>>();
    let n = s.len();
    let mut o = vec![];
    for i in 0..n {
        if s[i] == 'A' {
            o.push(i);
        }
    }
    let mut ans = 1;
    const MOD: i64 = 998_244_353;
    for i in 0..o.len() {
        ans *= (o[i] - i + 1) as i64;
        ans %= MOD;
    }
    println!("{ans}");
}