#ifndef ONLINE_JUDGE
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
using lint = long long;
using loub = long double;
template <typename T> using vec = vector<T>;
template <typename T> using deq = deque<T>;
template <typename T> using priq = priority_queue<T>;
template <typename T> using prig = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using uset = gp_hash_table<T, null_type>;
template <typename K, typename V> using umap = gp_hash_table<K, V>;
template <typename T> using iset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template <typename K, typename V> using imap = tree<K, V, less<K>, rb_tree_tag, tree_order_statistics_node_update>;
#define fst first
#define snd second
#define REP1(i, r) for (lint i = 0; i < (r); i++)
#define REP2(i, l, r) for (lint i = (l); i < (r); i++)
#define REP3(i, l, r, d) for (lint i = (l); (d) > 0 ? i < (r) : i > (r); i += (d))
#define SELECT_REP(_0, _1, _2, _3, REP_NAME, ...) REP_NAME
#define rep(...) SELECT_REP(__VA_ARGS__, REP3, REP2, REP1)(__VA_ARGS__)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define part(v, l, r) v.begin() + (l), v.begin() + (r)
#define rpart(v, l, r) make_reverse_iterator(v.begin() + (r)), make_reverse_iterator(v.begin() + (l))
template <typename T> void vecin(vec<T> &v, lint l, lint r) { rep(i, l, r) cin >> v[i]; }
template <typename T> void vecin(vec<T> &v) { vecin(v, 0, v.size()); };
template <typename T> void vecho(vec<T> &v, lint l, lint r) { rep(i, l, r) cout << (i > l ? " " : "") << v[i]; cout << endl; }
template <typename T> void vecho(vec<T> &v) { vecho(v, 0, v.size()); }
template <typename T> void echo(const T &val) { cout << val << endl; }
template <typename T, typename... Ts> void echo(const T &val, const Ts &...vals) { cout << val << " "; echo(vals...); }
template <typename T> int chmin(T &a, const T &b) { if (a <= b) return a == b; a = b; return 2; }
template <typename T> int chmax(T &a, const T &b) { if (a >= b) return a == b; a = b; return 2; }
template <typename T> T sq(T x) { return x * x; }
template <typename T> T cb(T x) { return x * x * x; }
const int INF = 2'000'000'001;
const lint LINF = 2'000'000'000'000'000'001;

void solve();
void test();
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << fixed << setprecision(15);
  int T = 1;
  // cin >> T;
  rep(i, T) {
    solve();
    // test();
  }
}

struct mod_calc {
  lint MOD = 998244353;
  vec<lint> FACT;
  vec<lint> FINV;

  mod_calc(lint mod) { MOD = mod; }

  lint pow(lint b, lint e) {
    lint ret = 1;
    while (e > 0) {
      if (e & 1) ret = ret * b % MOD;
      e >>= 1; b = b * b % MOD;
    }
    return ret;
  }

  lint inv(lint n) { return pow(n, MOD - 2); }

  void init_facts(lint MAX) {
    FACT.resize(MAX+1); FINV.resize(MAX+1);
    FACT[0] = 1;
    rep(i, 1, MAX+1) FACT[i] = i * FACT[i-1] % MOD;
    FINV[MAX] = inv(FACT[MAX]);
    rep(i, MAX, 0, -1) FINV[i-1] = i * FINV[i] % MOD;
  }

  lint fact(lint n) { return n >= 0 ? FACT[n] : 0; }
  
  lint finv(lint n) { return n >= 0 ? FINV[n] : 0; }

  lint bic(lint n, lint r) {
    return fact(n) * finv(r) % MOD * finv(n-r) % MOD;
  }
};

void solve() {
  lint N; string S;
  cin >> N >> S;

  mod_calc mc(998244353);
  mc.init_facts(N);

  lint K = count(all(S), 'A') + count(all(S), 'B');
  echo(mc.bic(N, K));
}