#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000000
#define Inf64 1000000000000000001LL

int main(){
	int n,m;
	cin>>n>>m;
	string s;
	cin>>s;
	mint t = 1;
	rep(i,s.size()){
		if(s[i]=='?')t *= 26;
	}
	mint iv = mint(26).inv();
	vector<vector<int>> E(n);
	rep(i,m){
		int a,b;
		cin>>a>>b;
		a--;b--;
		E[a].push_back(b);
		E[b].push_back(a);
	}
	mint ans = 0;
	rep(i,n){
		rep(j,E[i].size()){
			rep(k,E[i].size()){
				if(j==k)continue;
				mint tt = t;
				if(s[i]=='?')tt *= iv;
				else if(s[i]!='o')continue;
				if(s[E[i][j]]=='?')tt*=iv;
				else if(s[E[i][j]]!='i')continue;
				if(s[E[i][k]]=='?')tt*=iv;
				else if(s[E[i][k]]!='a')continue;
				ans += tt;
			}
		}
	}
	cout<<ans.val()<<endl;
	return 0;
}