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

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

    let mut pow_26 = [1usize; 6000];
    for i in 1..6000 {
        pow_26[i] = (pow_26[i - 1] * 26) % 998244353;
    }

    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);
}