import sys
from itertools import permutations
from heapq import heappop,heappush
from collections import deque
import random
import bisect

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

def check(N,M):
    domino = [[(0,0),(1,0),(2,0)],[(0,0),(0,1),(0,2)],[(0,0),(1,0),(1,1)],[(0,0),(0,1),(1,1)]]
    base = []

    for i in range(N):
        for j in range(M):
            for D in domino:
                b = 0
                for dx,dy in D:
                    if 0 <= i+dx < N and 0 <= j+dy < M:
                        b |= 1<<(M*(i+dx)+j+dy)
                    else:
                        break
                else:
                    for e in base:
                        b = min(b,b^e)
                    if b!=0:
                        base.append(b)
    
    return len(base)

mod = 998244353

def solve(N,M,S):
    B_cnt = [0] * 3
    F_cnt = [0] * 3
    for i in range(N):
        for j in range(M):
            if S[i][j] == "?":
                F_cnt[(i+j)%3] += 1
            elif S[i][j] == "B":
                B_cnt[(i+j)%3] ^= 1
    
    
    res = 0
    for p in range(2):
        tmp = 1
        for r in range(3):
            if B_cnt[r]!=p and F_cnt[r] == 0:
                tmp = 0
            elif F_cnt[r]!=0:
                tmp *= pow(2,F_cnt[r]-1,mod)
                tmp %= mod
        res += tmp
        res %= mod
    
    return res

N,M = mi()
S = [input() for i in range(N)]
print(solve(N,M,S))