N = int(input())
S = input()
mod = 998_244_353

ab = 0
cd = 0

for i,v in enumerate(S):
    if v == "A" or v == "B":
        ab+=1

def nCr(n,r,modulo):
    aa = 1
    bb = 1
    for i in range(r):
        aa = aa*(n-i)%modulo
        bb = bb*(i+1)%modulo
    #逆元
    inv =  pow(bb,modulo-2,modulo)

    return aa*inv%modulo

ans = nCr(N,ab,mod)

print(ans)