import sys
input = lambda: sys.stdin.readline().rstrip()
mod = 998244353

class Mod_Comb:
  def __init__(self, limit: int, mod: int):
    "O(limit)"
    # limit: limit C r.
    # if n is too large: limit = -1 and use ncr_2.
    # mod: prime.

    self.limit = limit
    self.mod = mod

    self.fact = [1, 1]
    self.factinv = [1, 1]
    self.inv = [0, 1]

    for i in range(2, self.limit+1):
      self.fact.append((self.fact[-1]*i % self.mod))
      self.inv.append((-self.inv[self.mod%i] * (self.mod // i)) % self.mod)
      self.factinv.append((self.factinv[-1] * self.inv[-1]) % self.mod)

  def div_mod(self, a: int, b: int) -> int:
    "Return (a // b % mod), mod:prime"
    if (a % b == 0):
      return a // b
    return (a % self.mod) * pow(b, self.mod-2, self.mod) % self.mod

  def ncr(self, n: int, r: int) -> int:
    "Return (nCr % mod)"
    "O(1), N <= 10**7"
    if r < 0 or n < r:
      return 0
    r = min(r, n-r)
    return self.fact[n] * self.factinv[r] * self.factinv[n-r] % self.mod

  def ncr_2(self, n: int, r: int) -> int:
    "O(r)"
    ret = 1
    r = min(r, n-r)
    for i in range(r):
      ret *= n - i
      ret %= self.mod
    for i in range(1, r+1):
      ret = self.div_mod(ret, i)
    return ret

#  -----------------------  #

n = int(input())
s = input()
cnt = s.count('A') + s.count('B')

mc = Mod_Comb(n, mod)
ans = mc.ncr(n, cnt)
print(ans)