mod = 998244353


def binomial_coefficient(n, r, mod=10**9+7):
    if r < 0 or r > n:
        return 0
    res = 1
    div = 1
    r = min(r, n - r)
    for i in range(r):
        res = res * (n - i) % mod
        div = div * (i + 1) % mod
    return res * pow(div, mod-2, mod) % mod


N = int(input())
S = input()

AB = S.count("A") + S.count("B")
print(binomial_coefficient(N, AB, mod))