import math

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

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

ans = math.factorial(N) * pow(math.factorial(ab),mod-2,mod) * pow(math.factorial(N-ab),mod-2,mod)
ans %= mod
print(ans)