#include<iostream>
#include<vector>
#include<cassert>
#include<atcoder/modint>
using namespace std;
using mint=atcoder::modint998244353;
int N,M;
string S;
vector<int>G[6000];
mint p3[6001];
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cin>>N>>M>>S;
	p3[0]=1;
	for(int i=1;i<=N;i++)p3[i]=p3[i-1]*mint::raw(26);
	int q=0;
	for(char c:S)if(c=='?')q++;
	for(int i=0;i<M;i++)
	{
		int a,b;cin>>a>>b;
		a--,b--;
		G[a].push_back(b);
		G[b].push_back(a);
	}
	mint ans=0;
	for(int i=0;i<N;i++)if(S[i]=='o'||S[i]=='?')
	{
		int nq=q;
		if(S[i]=='?')nq--;
		int ac=0,ic=0,qc=0;
		for(int v:G[i])
		{
			if(S[v]=='a')ac++;
			else if(S[v]=='i')ic++;
			else if(S[v]=='?')qc++;
		}
		{//ai
			ans+=mint::raw(ac)*mint::raw(ic)*p3[nq];
		}
		if(qc>=1)
		{//a?
			ans+=mint::raw(ac)*mint::raw(qc)*p3[nq-1];
		//?i
			ans+=mint::raw(qc)*mint::raw(ic)*p3[nq-1];
		}
		if(qc>=2)
		{
			ans+=mint::raw(qc)*mint::raw(qc-1)*p3[nq-2];
		}
	}
	cout<<ans.val()<<endl;
}