#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using II = pair<long long, long long>;
using VII = vector<II>;
using VVII = vector<VII>;
using VI = vector<long long>;
using VVI = vector<VI>;
using VVVI = vector<VVI>;
template <class T = long long>
inline bool chmax(T& a, const T& b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T = long long>
inline bool chmin(T& a, const T& b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T>
ostream& operator<<(ostream& s, const vector<T>& d) {
  for (long long i = 0, max_i = (d.size()); i < max_i; i++)
    s << d[i] << (i == d.size() - 1 ? "" : " ");
  return s;
}
template <class T>
ostream& operator<<(ostream& s, const vector<vector<T>>& d) {
  for (long long i = 0, max_i = (d.size()); i < max_i; i++)
    s << d[i] << (i == d.size() - 1 ? "" : "\n");
  return s;
}
template <class T, class S>
ostream& operator<<(ostream& s, const pair<T, S>& p) {
  s << "{" << p.first << ", " << p.second << "}";
  return s;
}
template <class T, class S>
ostream& operator<<(ostream& s, const map<T, S> m) {
  for (auto it = m.begin(); it != m.end(); it++) {
    s << *it << (next(it) == m.end() ? "" : "\n");
  }
  return s;
}
void dump_func() { cerr << endl; }
template <class Head, class... Tail>
void dump_func(Head&& h, Tail&&... t) {
  cerr << h << (sizeof...(Tail) == 0 ? "" : ", "),
      dump_func(forward<Tail>(t)...);
}
struct Fast {
  Fast() {
    cin.tie(0);
    ios::sync_with_stdio(false);
  }
} fast;
constexpr long long MOD = 998244353;
long long solve(string& s) {
  long long ans = 0;
  for (long long i = 0, max_i = (s.size()); i < max_i; i++) {
    for (long long j = (i + 1), max_i = (s.size()); j < max_i; j++) {
      char bef = -1;
      bool ok = true;
      for (long long k = 0, max_i = (s.size()); k < max_i; k++) {
        if (i <= k && k <= j) continue;
        if (bef == -1) {
          bef = s[k];
        } else {
          if (s[k] != bef) {
            ok = false;
            break;
          }
        }
      }
      if (ok) ans++;
    }
  }
  return ans;
}
signed main() {
  long long n;
  cin >> n;
  string s;
  cin >> s;
  long long l = 0;
  while (s[l] == s[0]) l++;
  long long r = 0;
  while (s.back() == s[n - 1 - r]) r++;
  ;
  long long ans;
  if (s[0] == s.back()) {
    ans = (l + 1) * (r + 1);
  } else {
    ans = l + r + 1;
  }
  cout << ans % MOD << endl;
}
