N = int(input())
S = input()
AB = S.count("A") + S.count("B")
M = 998244353
R1, R2 = 1, 1
for i in range(AB):
  R1 = R1 * (N - i) % M
  R2 = R2 * (i + 1) % M
print(R1 * pow(R2, M - 2, M) % M)