#include <bits/stdc++.h>
#include <atcoder/all>
#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/multiprecision/cpp_int.hpp>
namespace mp = boost::multiprecision;
using Bint = mp::cpp_int;
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
    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);
    }
    mint ans = 0;
    int cnt = 0;
    vector<mint> two(n+1,1);
    rep(i,n) two[i+1] = two[i]*26; 
    rep(i,n) if(s[i]=='?') cnt++;
    rep(i,n) {
        if(s[i]!='?' && s[i]!='o') continue;
        for(int v : g[i]) for(int u : g[i]) {
            if(u==v) continue;
            if((s[v]=='a' || s[v]=='?') && (s[u]=='i' || s[u]=='?')) {
                int tmp = cnt;
                if(s[v]=='?') tmp--;
                if(s[i]=='?') tmp--;
                if(s[u]=='?') tmp--;
                ans += two[tmp];
            }
        }
    }
    cout << ans.val() << endl;
    return 0;
}