n=int(input())
ab=0
cd=0
for c in input():
  ab+=c in "AB"
  cd+=c in "CD"
M=998244353
N=10**6
fa=[1]
for i in range(1,N+1):
  fa+=[fa[-1]*i%M]
fb=[pow(fa[N],M-2,M)]
for i in reversed(range(1,N+1)):
  fb+=[fb[-1]*i%M]
fb.reverse()
fc=lambda n,k:fa[n]*fb[k]*fb[n-k]%M if n>=k>=0 else 0
print(fc(ab+cd,ab))