#include<bits/stdc++.h>
using namespace std;
#define OVERLOAD_REP(_1, _2, _3, name, ...) name
#define REP1(i, n) for (auto i = std::decay_t<decltype(n)>{}; (i) != (n); ++(i))
#define REP2(i, l, r) for (auto i = (l); (i) != (r); ++(i))
#define rep(...) OVERLOAD_REP(__VA_ARGS__, REP2, REP1)(__VA_ARGS__)
#define REP(i, l, r) rep(i, l, r+1)
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
using ll = long long;
using ld = long double;
using P = pair<ll,ll>;
struct Edge {
  int to; ll w;
};
using Graph = vector<vector<int> >;
//using Graph = vector<vector<Edge> >;
const ll INF = 2e18;
//const int INF = 2e9;
template<class T> using vc = vector<T>;
template<class T> using vv = vector<vector<T> >;
template<class T> using vvv = vector<vector<vector<T> > >;
template<class T> using pq = priority_queue<T>;
template<class T> using pq_g = priority_queue<T, vc<T>, greater<T> >;
template<class T> istream& operator>>(istream& i, vc<T>& v) { rep(j, 0, v.size()) i>>v[j]; return i; }
template<class T> ostream& operator<<(ostream& o, vc<T>& v) { rep(j, 0, v.size()) o<<v[j]<<" "; return o; }
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 mod = 998244353;
vc<ll> fact;
ll modpow(ll x, ll n) {
  ll res = 1;
  while(n) {
    if(n&1) res = res * x % mod;
    x = x * x % mod;
    n >>= 1;
  }
  return res;
}

ll comb(ll n, ll r) {
  return fact[n]*modpow(fact[r]*fact[n-r]%mod, mod-2)%mod;
}

int main() {
  // 高速化
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  // 小数点の出力桁数を指定
  cout << fixed << setprecision(10);
  // メイン
  int N;string S;
  cin>>N>>S;

  // calc factorial
  fact.resize(600000);
  fact[0] = 1;
  rep(i, 1, 600000) {
    fact[i] = fact[i-1] * i % mod;
  }

  bool Agata = S[0]==S[1];
  ll ans = 0;
  if(Agata) {
    int han = N/2;
    REP(i, 0, han) ans = (ans + comb(han, i)*comb(han, i)) % mod;
  } else {
    // 2^(N/2)
    ans = modpow(2, N/2);
  }
  cout << ans << endl;


  return 0;
}