import math

N = int(input())
S = input()
mod = 998244353

ab = 0
for s in S:
    if s == 'A' or s == 'B':
        ab += 1

def modinv(x):
    return pow(math.factorial(x),mod-2,mod)

ans = modinv(ab) * modinv(N-ab)
for i in range(N):
    ans *= i+1
    ans %= mod
    
print(ans)