N=int(input())
S=input().strip()
n_ab=0
for s in S:
    if s in "AB":
        n_ab+=1
n_cd = N-n_ab
def combo(n, k, mod=998244353):
    def fact(n,k=0):
        a=1
        for i in range(k+1,n+1):
            a=a * i % mod
        return a
    k=min(k,n-k)
    a=fact(n, n-k) # (n-k)!
    b=fact(k) # k!
    return (a * pow(b, mod-2, mod)) % mod
print(combo(N, n_ab))