class combination():
    def __init__(self,N,p):#Nは上限,pはmod
        self.fact = [1,1]
        self.factinv = [1,1]
        self.inv = [0,1]
        for i in range(2, N + 1):
            self.fact.append((self.fact[-1] * i) % p)
            self.inv.append((-self.inv[p % i] * (p // i)) % p)
            self.factinv.append((self.factinv[-1] * self.inv[-1]) % p)
    def cmb(self,n, r,p):
        if (r < 0) or (n < r):
            return 0
        r = min(r, n - r)
        return self.fact[n] * self.factinv[r] * self.factinv[n-r] % p
mod = 998244353
C = combination(10**6,mod)
N = int(input())
S = list(input())
g1 = 0
for s in S:
    if s == 'A' or s == 'B':
        g1 += 1
ans = C.cmb(N,g1,mod)
print(ans)