// g++-15 1.cpp -std=c++23 -O2 -I .
#include <bits/stdc++.h>
using namespace std;

#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

// #include<ext/pb_ds/assoc_container.hpp>
// #include<ext/pb_ds/tree_policy.hpp>
// #include<ext/pb_ds/tag_and_trait.hpp>
// using namespace __gnu_pbds;

// #include <atcoder/lazysegtree>
// using namespace atcoder;

using ll = long long;
using ld = long double;
 
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vld = vector<ld>;
using vvld = vector<vld>;
using vst = vector<string>;
using vvst = vector<vst>;

#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define pq_big(T) priority_queue<T,vector<T>,less<T>>
#define pq_small(T) priority_queue<T,vector<T>,greater<T>>
#define all(a) a.begin(),a.end()
#define rep(i,start,end) for(ll i=start;i<(ll)(end);i++)
#define per(i,start,end) for(ll i=start;i>=(ll)(end);i--)
#define uniq(a) sort(all(a));a.erase(unique(all(a)),a.end())

random_device seed;
mt19937_64 randint(seed());

ll grr(ll mi, ll ma) { // [mi, ma)
    return mi + randint() % (ma - mi);
}

constexpr ll mod = 998244353;

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int n,m;cin>>n>>m;
  vst g(n);
  rep(i,0,n)cin>>g[i];
  vll two(n*m+10,1);
  rep(i,1,n*m+10){
    two[i]=two[i-1]*2;
    two[i]%=mod;
  }
  ll ev=1,od=1;
  vi q(3,0),c(3,0);
  rep(i,0,n){
    rep(j,0,m){
      int tar=(i+j)%3;
      if(g[i][j]=='B'){
        c[tar]^=1;
      }
      if(g[i][j]=='?'){
        q[tar]++;
      }
    }
  }
  rep(i,0,3){
    ll stay=1,change=0;
    if(q[i]>0){
      stay=two[q[i]-1],change=two[q[i]-1];
    }
    if(c[i]==0){
      ev*=stay,od*=change;
    }
    else{
      ev*=change,od*=stay;
    }
    ev%=mod;
    od%=mod;
  }
  cout<<(ev+od)%mod<<endl;
}