#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
//using mint = modint1000000007;
using ll = long long;
using ld = long double;
using pll = pair<ll, ll>;
using tlll = tuple<ll, ll, ll>;
constexpr ll INF = 1LL << 60;
template<class T> bool chmin(T& a, T b) {if (a > b) {a = b; return true;} return false;}
template<class T> bool chmax(T& a, T b) {if (a < b) {a = b; return true;} return false;}
ll safemod(ll A, ll M) {return (A % M + M) % M;}
ll divfloor(ll A, ll B) {if (B < 0) {return divfloor(-A, -B);} return (A - safemod(A, B)) / B;}
ll divceil(ll A, ll B) {if (B < 0) {return divceil(-A, -B);} return divfloor(A + B - 1, B);}
#define FINALANS(A) do {cout << (A) << '\n'; exit(0);} while (false)

int main()
{
  ll N;
  string S;
  cin >> N >> S;

  vector dp(N + 1, vector(2, vector(2, mint(0))));
  dp.at(0).at(0).at(0) = 1;
  for (ll i = 0; i < N; i++)
  {
    for (ll b1 = 0; b1 < 2; b1++)
    {
      for (ll b2 = 0; b2 < 2; b2++)
      {
        for (char c = 'a'; c <= 'z'; c++)
        {
          ll nb1 = b1 + (c == 'a' ? 1 : 0);
          if (nb1 == 2)
            continue;

          ll nb2;
          if (c < S.at(i))
          {
            nb2 = 1;
          }
          else if (c == S.at(i))
          {
            nb2 = b2;
          }
          else
          {
            if (b2 == 0)
              continue;
            nb2 = 1;
          }

          dp.at(i + 1).at(nb1).at(nb2) += dp.at(i).at(b1).at(b2);
        }
      }
    }
  }

  mint ans = dp.at(N).at(1).at(1);
  cout << ans.val() << endl;

  /*
  for (ll i = 0; i < N + 1; i++)
  {
    for (ll b1 = 0; b1 < 2; b1++)
    {
      for (ll b2 = 0; b2 < 2; b2++)
      {
        cerr << i << " " << b1 << " " << b2 << "  " << dp.at(i).at(b1).at(b2).val() << endl;
      }
    }
  }
  //*/
}