#include <bits/stdc++.h>
using namespace std;
 
#include <atcoder/all>
using namespace atcoder;
 
#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
 
#define FASTIO cin.tie(0)->sync_with_stdio(0)
 
using ll = long long;
using mint = modint998244353;

int main() {
  FASTIO;
  int N, M;
  string S;
  cin >> N >> M >> S;
  vector<vector<int>> G(N);
  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);
  }
  int q = 0;
  for(int i = 0; i < N; ++i) {
    if(S[i] == '?') ++q;
  }
  vector<mint> pw(N + 1, 1);
  for(int i = 0; i < N; i++) {
    pw[i + 1] = pw[i] * 26;
  }
  mint ans;
  for(int i = 0; i < N; i++) {
    if(S[i] != 'o' && S[i] != '?') continue;
    mint a = 0, b = 0; int n = 0;
    for(int j : G[i]) {
      if(S[j] == 'a') a++;
      if(S[j] == 'i') b++;
      if(S[j] == '?') n++;
    }
    int q2 = q - n - (S[i] == '?');
    if(n == 0) {
      ans += pw[q2] * a * b;
    }else if(n == 1) {
      ans += pw[q2] * (24 * a * b + (a + 1) * b + a * (b + 1));
    }else {
      ans += pw[q2] * pw[n - 2] * (26 * a * (26 * b + n) + n * (26 * b + n - 1));
    }
  }
  cout << ans.val() << endl;
}