import std;

void main() {
    ulong N;
    readf("%d\n", N);

    auto S = readln.chomp;

    ulong M = 998_244_353;

    ulong cntAB = S.count!(s => (s == 'A' || s == 'B'));

    ulong res = 1;
    foreach (i; 0 .. cntAB) {
        res = (res * (N - i)) % M;
        res = (res * powmod(i+1, M-2, M)) % M;
    }

    res.writeln;
}