using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static long NN => long.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, m) = (c[0], c[1]);
        var s = ReadLine();
        var map = NArr(m);
        var mod = 998_244_353;
        var q = s.Count(si => si == '?');
        var all = Exp(26, q, mod);
        var rev = Exp(26, mod - 2, mod);
        var r2 = rev * rev % mod;
        var r3 = r2 * rev % mod;
        var ans = 0L;
        var tree = new List<int>[n];
        for (var i = 0; i < tree.Length; ++i) tree[i] = new List<int>();
        foreach (var edge in map)
        {
            tree[edge[0] - 1].Add(edge[1] - 1);
            tree[edge[1] - 1].Add(edge[0] - 1);
        }
        for (var i = 0; i < n; ++i)
        {
            if (s[i] == 'o' || s[i] == '?')
            {
                var ac = 0L;
                var ic = 0L;
                var qc = 0L;
                foreach (var next in tree[i])
                {
                    if (s[next] == 'a') ++ac;
                    else if (s[next] == 'i') ++ic;
                    else if (s[next] == '?') ++qc;
                }
                if (s[i] == 'o')
                {
                    ans = (ans + ac * ic % mod * all % mod) % mod;
                    ans = (ans + ac * qc % mod * all % mod * rev % mod) % mod;
                    ans = (ans + ic * qc % mod * all % mod * rev % mod) % mod;
                    ans = (ans + qc * (qc - 1) % mod * all % mod * r2 % mod) % mod;
                }
                else
                {
                    ans = (ans + ac * ic % mod * all % mod * rev % mod) % mod;
                    ans = (ans + ac * qc % mod * all % mod * r2 % mod) % mod;
                    ans = (ans + ic * qc % mod * all % mod * r2 % mod) % mod;
                    ans = (ans + qc * (qc - 1) % mod * all % mod * r3 % mod) % mod;
                }
            }
        }
        WriteLine(ans);
    }
    static long Exp(long n, long p, int mod)
    {
        long _n = n % mod;
        var _p = p;
        var result = 1L;
        if ((_p & 1) == 1) result *= _n;
        while (_p > 0)
        {
            _n = _n * _n % mod;
            _p >>= 1;
            if ((_p & 1) == 1) result = result * _n % mod;
        }
        return result;
    }
}