#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using mint = atcoder::modint998244353;
int main () {
	int N, M;
	cin >> N >> M;
	string s;
	cin >> s;
	int nh = 0;
	for (auto& a : s) nh += (a == '?');
	std::vector<vector<int>> gr(N);
	for (int i = 0; i < M; i ++) {
		int a, b;
		cin >> a >> b;
		gr[--a].push_back(--b);
		gr[b].push_back(a);
	}
	mint ans = 0;
	mint pw = 26;
	mint ai = pw.pow(nh), hi = pw.pow(nh - 1), hh = pw.pow(nh - 2);
	mint iv = pw.inv();
	for (int i = 0; i < N; i ++) {
		mint ca = 0, ci = 0, ch = 0;
		if ((s[i] != 'o') && (s[i] != '?')) continue;
		for (auto& j : gr[i]) {
			if (s[j] == 'a') {
				ca ++;
			} else if (s[j] == 'i') {
				ci ++;
			} else if (s[j] == '?') {
				ch ++;
			}
		}
		mint pl = ca * ci * ai + (ca * ch + ch * ci) * hi + (ch * (ch - 1)) * hh;
		if (s[i] == '?') pl *= iv;
		ans += pl;
	}
	cout << ans.val() << endl;
}