n=int(input())
s=input()
cnt=0
for i in s:
  if i=='A' or i=='B':
    cnt+=1
    

mod=998244353
#nCr mod p
M=(10**5)*5+1 
fac=[1]*M
ninv=[1]*M
finv=[1]*M
for i in range(2,M):
  fac[i]=fac[i-1]*i%mod
  ninv[i]=(-(mod//i)*ninv[mod%i])%mod
  finv[i]=finv[i-1]*ninv[i]%mod

def comb(n,k):
  if k>n:
    return 0
  return (fac[n]*finv[k]%mod)*finv[n-k]%mod

print(comb(n,cnt))