n = int(input())
fac_arr = [1] * (n+1)
r_s_fac_arr = [1] * (n+1)
mod = 998244353
for i in range(1,n+1):
    fac_arr[i] = (fac_arr[i-1] % mod) * i % mod
    r_s_fac_arr[i] = (r_s_fac_arr[i-1] % mod) * pow(i,mod-2,mod) % mod 
def nckMod(n,k):
    return fac_arr[n]  % mod *  r_s_fac_arr[k] % mod * r_s_fac_arr[n-k] % mod
def npkMod(n,k):
    return fac_arr[n]  % mod * r_s_fac_arr[n-k] % mod


s = input()
from collections import Counter
c = Counter(s)
mod = 998244353
print(nckMod(n,c["A"]+c["B"]))