class Combination:
    def __init__(self, N, mod = 10**9+7):
        self.mod = mod
        self.fact = [0] * (N+1)
        self.factinv = [0] * (N+1)
        self.fact[0] = 1
        self.factinv[0] = 1
        for i in range(1,N+1):
            self.fact[i] = (i * self.fact[i-1]) % self.mod
            self.factinv[i] = self.BinPower(self.fact[i], self.mod - 2)

    def BinPower(self, x, k):
        ret = 1
        while k > 0:
            if k & 1:
                ret = ret * x % self.mod
            x = x * x % self.mod
            k >>= 1
        return ret

    def ncr(self, n, r):
        if n < r or r < 0:
            return 0
        return (self.fact[n] * self.factinv[r] % self.mod) * self.factinv[n-r] % self.mod

mod = 998244353
N = int(input())
S = input()
cnt = 0
for i in range(N):
    if S[i] == 'A' or S[i] == 'B':
        cnt += 1
C = Combination(N, mod)
print(C.ncr(N, cnt))