use proconio::{
    input,
    marker::{Chars, Usize1},
};

fn main() {
    input! {
        n: usize,
        m: usize,
        s: Chars,
        ab: [(Usize1, Usize1); m],
    }

    let mut graph = vec![vec![]; n];
    for (a, b) in ab {
        graph[a].push(b);
        graph[b].push(a);
    }

    let question_count = s.iter().filter(|&&x| x == '?').count();
    let mut ans = 0;

    for center in 0..n {
        let question_count = match s[center] {
            'o' => question_count,
            '?' => question_count - 1,
            _ => continue,
        };

        for &head in &graph[center] {
            let question_count = match s[head] {
                'a' => question_count,
                '?' => question_count - 1,
                _ => continue,
            };

            for &tail in &graph[center] {
                if head == tail {
                    continue;
                }

                let question_count = match s[tail] {
                    'i' => question_count,
                    '?' => question_count - 1,
                    _ => continue,
                };

                ans += pow(26, question_count);
                ans %= 998244353;
            }
        }
    }
    println!("{}", ans);
}

fn pow(mut n: usize, mut m: usize) -> usize {
    let mut r = 1;
    while m > 0 {
        if m & 1 == 1 {
            r *= n;
            r %= 998244353;
        }
        n *= n;
        n %= 998244353;
        m >>= 1;
    }
    r
}