N = int(input())
S = input()
AB = S.count("A") + S.count("B")
A1, A2 = 1, 1
for i in range(AB):
    A1 *= (N - i) % 998244353
    A2 *= (i + 1) %998244353
print(A1 * pow(A2, 998244351, 998244353) % 998244353)