typedef long long ll;
typedef long double ld;
#include <bits/stdc++.h>
using namespace std;
#define int long long

const int MAX = 510000;
const int MOD = 998244353;

long long fac[MAX], finv[MAX], inv[MAX];
void COMinit(){
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}
long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

signed main(){
    COMinit();
    ll n;
    std::cin >> n;
    string s;
    std::cin >> s;
    ll cnt = 0;
    for (int i = 0; i < n; i++) {
        if(s[i]=='A'||s[i]=='B'){
            cnt++;
        }
    }
    std::cout << COM(n,cnt) << std::endl;
}