#include <iostream>
#include <vector>
#include <atcoder/modint>

using mint = atcoder::modint998244353;

int main() {
    int N;
    std::string S;
    std::cin >> N >> S;
    int M = 0;
    for (char c : S) M += c == 'A' || c == 'B';

    std::vector<mint> fact(N + 1, 1);
    for (int i = 2; i <= N; i++) fact[i] = fact[i - 1] * i;
    std::vector<mint> ifact(N + 1, 1);
    ifact[N] = fact[N].inv();
    for (int i = N; i > 2; i--) ifact[i - 1] = ifact[i] * i;
    mint result = fact[N] * ifact[M] * ifact[N - M];
    std::cout << result.val() << std::endl;
}