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

MOD = 998244353
fact = [1]*(N+1)
rfact = [1]*(N+1)
r = 1
for i in range(1, N+1):
    fact[i] = r = r * i % MOD
rfact[N] = r = pow(fact[N], MOD-2, MOD)
for i in range(N, 0, -1):
    rfact[i-1] = r = r * i % MOD

# nCk (mod MOD) を求める
def comb(n, k):
    return fact[n] * rfact[k] * rfact[n-k] % MOD

AB = 0
CD = 0
for i in range(N):
    if S[i] == "A" or S[i] == "B":
        AB += 1
print(comb(N,AB))