from collections import Counter

n = int(input())
S = list(input())
mod = 998244353

fact = [1] * (n + 1)
inv = [1] * (n + 1)
finv = [1] * (n + 1)
for i in range(2, n + 1):
    fact[i] = fact[i - 1] * i % mod
    inv[i] = mod - inv[mod % i] * (mod // i) % mod
    finv[i] = finv[i - 1] * inv[i] % mod
def comb(x, y):
    return (fact[x] * finv[y] % mod) * finv[x - y] % mod

counter = Counter(S)
print(comb(n, counter['A'] + counter['B']))