import io
import sys
from collections import defaultdict, deque, Counter
from itertools import permutations, combinations, accumulate
from heapq import heappush, heappop
from bisect import bisect_right, bisect_left
from math import gcd
import math
from sys import stdout

_INPUT = """\
6
3 4
??BW
WBBW
WWWW
3 3
WWW
WBW
BBW
12 30
WW?W?BW??B??WBWBW?WWWWB?WBWWWW
BBB?WBBWWBBWW?WW?BWBWW?WBWW?WW
WBBBW?BW?WB?BWBWWWBBBWWWWB??WB
WW?WWBWWWWB?B?BBBWB?BBB?BB?W??
B?BB?WWBWWBW?BWBBBWWBBBB??B??B
WWBWWBWBWWW??W?WBBBWWWWW?WW?WW
WWWBB?B?BWB?WBWBW?W?BBBWB?WBBW
??BBWWBWW?WWBBBW?WWBWW?BWBBBWW
WBW?WW?B??BW?BWWBBBW?WWWWB??BB
W?BW?BWWBB?BW??BWWWWBB??BW?BWB
?WWW?WB?WWBBBWWBBBWWBW?BBWW?BB
?WWWBWBBWWWBWWWBBWWWB?WW?BWBWB
"""

def input():
  return sys.stdin.readline()[:-1]

mod=998244353
def solve(test):
  N,M=map(int, input().split())
  S=[input() for _ in range(N)]
  ans=[[0]*2 for _ in range(3)]
  for i in range(N):
    for j in range(M):
      if S[i][j]=='B':
        ans[(i+j)%3][0]^=1
      elif S[i][j]=='?':
        ans[(i+j)%3][1]+=1
  even=1
  for i in range(3):
    if ans[i][1]==0:
      if ans[i][0]==1: even=0; break
      else: continue
    else: even*=pow(2,ans[i][1]-1,mod); even%=mod
  odd=1
  for i in range(3):
    if ans[i][1]==0:
      if ans[i][0]==0: odd=0; break
      else: continue
    else: odd*=pow(2,ans[i][1]-1,mod); odd%=mod
  print((even+odd)%mod)

def random_input():
  from random import randint,shuffle
  N=randint(1,10)
  M=randint(1,N)
  A=list(range(1,M+1))+[randint(1,M) for _ in range(N-M)]
  shuffle(A)
  return (" ".join(map(str, [N,M]))+"\n"+" ".join(map(str, A))+"\n")*3

def simple_solve():
  return []

def main(test):
  if test==0:
    solve(0)
  elif test==1:
    sys.stdin = io.StringIO(_INPUT)
    case_no=int(input())
    for _ in range(case_no):
      solve(0)
  else:
    for i in range(1000):
      sys.stdin = io.StringIO(random_input())
      x=solve(1)
      y=simple_solve()
      if x!=y:
        print(i,x,y)
        print(*[line for line in sys.stdin],sep='')
        break

#0:提出用、1:与えられたテスト用、2:ストレステスト用
main(0)