#include <bits/stdc++.h>
using namespace std;
const long long MOD = 998244353;
int main(){
  int N;
  cin >> N;
  string S;
  cin >> S;
  vector<vector<vector<long long>>> dp(N + 1, vector<vector<long long>>(2, vector<long long>(2, 0)));
  dp[0][0][0] = 1;
  for (int i = 0; i < N; i++){
    for (int j = 0; j < 2; j++){
      for (int k = 0; k < 2; k++){
        for (int l = 0; l < 26; l++){
          if (j == 0 && l > S[i] - 'a'){
            continue;
          }
          if (k == 1 && l == 0){
            continue;
          }
          int j2 = j;
          if (l < S[i] - 'a'){
            j2 = 1;
          }
          int k2 = k;
          if (l == 0){
            k2++;
          }
          dp[i + 1][j2][k2] += dp[i][j][k];
          dp[i + 1][j2][k2] %= MOD;
        }
      }
    }
  }
  cout << dp[N][1][1] << endl;
}