#include <bits/stdc++.h>
using namespace std;
#include<atcoder/all>
using mint = atcoder::modint998244353;
using ld = long double;
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define chmax(a,b) a=max(a,b)
#define chmin(a,b) a=min(a,b)

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int N,M;
    cin>>N>>M;
    string S;
    cin>>S;
    vector<vector<int>> G(N);
    rep(i,M){
        int a,b;
        cin>>a>>b;
        a--;b--;
        G[a].push_back(b);
        G[b].push_back(a);
    }
    int hc=0;
    rep(i,N) if(S[i]=='?') hc++;
    mint ans=0;
    vector<mint> p(N+1,1);
    rep(i,N) p[i+1]=p[i]*26;
    rep(i,N){
        if(S[i]=='o'||S[i]=='?'){
            int d=(S[i]=='?');
            for(int a: G[i]){
                for(int b: G[i]){
                    if(a==b) continue;
                    if(S[a]=='?'&&S[b]=='?') ans+=p[hc-2-d];
                    else if(S[a]=='a'&&S[b]=='i') ans+=p[hc-d];
                    else if(S[a]=='a'&&S[b]=='?') ans+=p[hc-1-d];
                    else if(S[a]=='?'&&S[b]=='i') ans+=p[hc-1-d];
                }
            }
        }
    }
    cout<<ans.val()<<"\n";
}