#include <bits/stdc++.h>
#include <bits/stdc++.h>
#include <bits/stdc++.h>
using namespace std;
#include <atcoder/modint>
using namespace atcoder;
using mint = modint998244353;
using ll = long long;
#define fix(x) fixed << setprecision(x)
#define rep(i, n) for(int i = 0; i < n; ++i)
#define all(x) (x).begin(),(x).end()
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;}
constexpr ll INFLL = (1LL << 62), MOD = 998244353;
constexpr int INF = (1 << 30);

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n,m;
    string s;
    cin >> n >> m >> s;
    vector<mint> ca(n,0), ci(n,0), cq(n,0);
    mint t = 26, ans = 0;
    int cnt = 0;
    rep(i,n) cnt += (s[i]=='?');
    rep(i,m){
        int u,v;
        cin >> u >> v;
        --u, --v;
        if(s[u]=='a') ++ca[v];
        if(s[u]=='i') ++ci[v];
        if(s[u]=='?') ++cq[v];
        if(s[v]=='a') ++ca[u];
        if(s[v]=='i') ++ci[u];
        if(s[v]=='?') ++cq[u];
    }
    rep(i,n){
        if(s[i]=='o'){
            ans += ca[i]*ci[i]*t.pow(cnt);
            if(cnt>=1) ans += (ca[i] + ci[i])*cq[i]*t.pow(cnt-1);
            if(cnt>=2) ans += cq[i]*(cq[i]-1)*t.pow(cnt-2);
        }
        if(s[i]=='?'){
            ans += ca[i]*ci[i]*t.pow(cnt-1);
            if(cnt>=2) ans += (ca[i] + ci[i])*cq[i]*t.pow(cnt-2);
            if(cnt>=3) ans += cq[i]*(cq[i]-1)*t.pow(cnt-3);
        }
    }
    cout << ans.val() << '\n';
    return 0;
}