def main():
    N = int(input())
    S = input()
    M = S.count('A') + S.count('B')

    ans = 1
    for i in range(M):
        ans = ans * (N-i) * pow(i+1, -1, 998244353)
        ans %= 998244353

    print(ans)


if __name__ == '__main__':
    main()