#include <bits/stdc++.h>
#include <atcoder/modint>
#define rep(i,n) for(int i = 0; i < (int)(n); i++)

using namespace std;
using namespace atcoder;
using LL = long long;
using mint = modint998244353;

int main(){
    int N;
    string S;
    cin >> N >> S;
    int num = 0;
    rep(i,N) if(S[i] == 'A' || S[i] == 'B') num++;
    mint ans = 1;
    rep(i,num){
        ans *= N - i;
        ans /= i + 1;
    }
    cout << ans.val() << endl;
    
    return 0;
}