#include <bits/stdc++.h>
using namespace std;

#ifdef _RUTHEN
#include "debug.hpp"
#else
#define show(...) true
#endif

using ll = long long;
#define rep(i, n) for (int i = 0; i < (n); i++)
template <class T> using V = vector<T>;

#include <atcoder/modint>
using mint = atcoder::modint998244353;

template <class Mint> Mint binomial(long long N, long long K) {
    if (N < 0 || K < 0 || N < K) return 0;
    Mint ret1 = 1, ret2 = 1;
    K = min(K, N - K);
    for (long long i = 1; i <= K; i++) {
        ret1 *= N--;
        ret2 *= i;
    }
    return ret1 / ret2;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N;
    cin >> N;
    string S;
    cin >> S;
    int cnt = 0;
    for (auto c : S) cnt += (c == 'A' || c == 'B');
    cout << binomial<mint>(N, cnt).val() << '\n';
    return 0;
}