#include<iostream>
#include<vector>
#include<cassert>
using namespace std;

long long modpow(long long a, long long n, long long m)
{
	assert(m>=1);
	if(a==0) return 0LL;
	long long res = 1;
	while(n > 0)
	{
		if(n&1) res = res * a % m;
		a = a * a % m;
		n >>= 1;
	}
	return res;
}
const long long MOD = 998244353;
int main()
{
	int N,M;string S;
	cin >> N >> M >> S;
	long long q_count = 0;
	for(char c : S) if(c=='?') q_count++;
	vector<vector<int>> G(N);
	for(int i=0;i<M;++i)
	{
		int u,v;
		cin >> u >> v;
		--u,--v;
		G[u].emplace_back(v);
		G[v].emplace_back(u);
	}

	string check = "ai?";
	long long ans = 0;
	for(int u=0;u<N;++u)
	{
		if(S[u] == 'o' || S[u] == '?')
		{
			vector<int> vertexes;
			string str = "";
			vector<long long> count(3);
			for(int v : G[u])
			{
				vertexes.emplace_back(v);
				for(int i=0;i<3;++i) if(check[i] == S[v]) count[i]++;
			}
			long long q = S[u]=='?' ? q_count-1 : q_count;
			ans += count[0] * count[1] % MOD * modpow(26,q,MOD) % MOD;
			ans %= MOD;
			ans += count[0] * count[2] % MOD * modpow(26,q,MOD) % MOD;
			ans %= MOD;
			ans += count[1] * count[2] % MOD * modpow(26,q,MOD) % MOD;
			ans %= MOD;

			ans += count[2]*(count[2]-1) % MOD * modpow(26,q-count[2],MOD) % MOD;
			ans %= MOD;
		}
	}

	cout << ans << endl;
}