MOD = 998244353

n = int(input())
S = input()
a = 0
for s in S:
    if s == "A" or s == "B":
        a += 1

ans = 1
for i in range(n, n - a, -1):
    ans *= i
    ans %= MOD
inv = 1
for i in range(1, a + 1):
    inv *= i
    inv %= MOD
ans *= pow(inv, MOD - 2, MOD)
print(ans % MOD)