mod = 998244353
comb_num = 10**6 + 2
F = [1] * comb_num
F_ = [1] * comb_num
for i in range(2, comb_num): F[i] = F[i-1]*i%mod
F_[-1] = pow(F[-1], -1, mod)
for i in range(comb_num-1, 0, -1): F_[i-1] = F_[i]*i%mod
def comb(a, b):
    if 0 <= b <= a: return F[a] * F_[b] * F_[a-b] % mod
    else: return 0
def main():
    n = int(input())
    S = input()
    a0 = a1 = 0
    for s in S:
        if s in "AB":
            a0 += 1
        else:
            a1 += 1
    return comb(a0+a1, a0)
print(main())