#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 1000000000000000001


int main(){
	
	int h,w;
	cin>>h>>w;
	
	vector<string> s(h);
	rep(i,h)cin>>s[i];
	vector<pair<int,int>> p;
	rep(i,h){
		rep(j,w){
			if(s[i][j]=='?'){
				
			}
			else if(s[i][j]=='B')s[i][j] = '1';
			else s[i][j] = '0';
		}
	}
	vector<mint> dp(4,0);
	dp[0] = 1;
	rep(i,h){
		vector<mint> tdp(4,0);
		tdp[0] = 1;
		rep(j,w-2){
			vector<mint> ndp(4,0);
			rep(k,2){
				if(s[i][j]=='?'||s[i][j]==k+'0'){
					rep(l,4){
						int cur = k;
						cur ^= l&1;
						int nl = l;
						if(cur){
							nl ^= 7;
						}
						nl >>= 1;
						ndp[nl] += tdp[l];
					}
					
				}
			}
			swap(tdp,ndp);
		}
		vector<mint> ndp(4,0);
		rep(j,4){
			rep(k,4){
				int nxt = j^k;
				rep(m,2){
					if(s[i][w-2]!='?'&&s[i][w-2]!=m+'0')continue;
					rep(n,2){
						if(s[i][w-1]!='?'&&s[i][w-1]!=n+'0')continue;
						nxt ^= m;
						nxt ^= n<<1;
						int nk;
						if(nxt==0)nk = 0;
						if(nxt==1)nk = 3;
						if(nxt==2)nk = 1;
						if(nxt==3)nk = 2;
						ndp[nk] += tdp[k]*dp[j];
					}
				}
			}
		}
		swap(dp,ndp);
	}
	cout<<dp[0].val()<<endl;
    return 0;
}