const MOD: usize = 998244353;

fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    let s = s.trim().chars().map(|c| c as usize - 'a' as usize).collect::<Vec<usize>>();

    let mut edp = vec![vec![0usize; 2]; n+1];
    let mut ldp = vec![vec![0usize; 2]; n+1];
    edp[1][if s[0] == 0 { 1 } else { 0 }] = 1;
    ldp[1][0] = if s[0] > 1 { s[0] - 1 } else { 0 };
    ldp[1][1] = if s[0] != 0 { 1 } else { 0 };
    for i in 1..n {
        if s[i] == 0 {
            edp[i+1][1] += edp[i][0];
        } else {
            edp[i+1][0] += edp[i][0];
            edp[i+1][1] += edp[i][1];
        }
        ldp[i+1][0] += ldp[i][0] * 25 % MOD;
        ldp[i+1][1] += ldp[i][1] * 25 % MOD + ldp[i][0];
        if s[i] > 0 {
            ldp[i+1][0] += edp[i][0] * (s[i] - 1) % MOD;
            ldp[i+1][1] += edp[i][0];
            ldp[i+1][1] += edp[i][1] * (s[i] - 1) % MOD;
        }
        ldp[i+1][0] %= MOD;
        ldp[i+1][1] %= MOD;
    }
    println!("{}", ldp[n][1]);
}