N,M=map(int, input().split())
# D=[[] for i in range(N)]
# for i in range(M):
#   a,b,d=map(int, input().split())
#   a-=1;b-=1
#   D[a].append((d,b));D[b].append((d,a))

A,B=[0]*3,[0]*3
for i in range(N):
  S=input()
  for j in range(M):
    if S[j]=='?':
      A[(i+j)%3]+=1 
    elif S[j]=='B':
      B[(i+j)%3]+=1 

mod=998244353;n=10**6+100
inv_t=[0]+[1]
for i in range(2,n):
  inv_t+=[inv_t[mod%i]*(mod-int(mod/i))%mod]

kai=[1,1]
rev_kai=[1,inv_t[1]]
for i in range(2,n):
  kai.append(kai[-1]*i%mod)
  rev_kai.append(rev_kai[-1]*inv_t[i]%mod)

def cmb(n,r):
  return kai[n]*rev_kai[r]*rev_kai[n-r]%mod

C=[[0,0,0] for i in range(2)]

for i in range(3):
  for j in range(A[i]+1):
    c=cmb(A[i],j)
    C[(B[i]+j)%2][i]+=c 
    C[(B[i]+j)%2][i]%=mod 

ans=0
for i in range(2):
  p,q,r=C[i]
  p*=q 
  p%=mod 
  p*=r 
  p%=mod 
  ans+=p
print(ans%mod)