#include <bits/stdc++.h>
using namespace std;
void _main();
int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	_main();
	return 0;
}
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using vi = std::vector<int>;
using vvi = std::vector<vi>;
using vl = std::vector<ll>;
using vii = std::vector<pair<int, int> >;
using vvl = std::vector<vl>;
using vll = std::vector<pair<ll , ll> >;
using vd = std::vector<double>;
using vvd = std::vector<vd>;
using vs = std::vector<std::string>;
using vvs = std::vector<vs>;
using vb = std::vector<bool>;
using vvb = std::vector<vb>;
using vc = std::vector<char>;
using vvc = std::vector<vc>;
using pii = std::pair<int, int>;
using pll = std::pair<ll, ll>;
using piil = std::pair<pair<int, int>, ll>;
using mii = std::map<int, int>;
using mll = std::map<ll, ll>;
using pql = std::priority_queue<ll>;
using pqi = std::priority_queue<int>;
using pqiil = std::priority_queue<pair<pair<int, int>, ll> >;
using pqii = std::priority_queue<pair<int, int> >;

#define pb push_back
#define ps push
#define eb emplace_back
#define is insert
#define er erase
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define sf(i) sizeof(i)
#define endl "\n"
#define sz(v) ((int)(v).size())
#define all(v) (v).begin(), (v).end()
#define rep(i, L, R) for(ll i = L;i<=R;i++)
#define pcis precision

template<typename T>
struct infinity {
	static constexpr T max=std::numeric_limits<T>::max();
	static constexpr T min=std::numeric_limits<T>::min();
	static constexpr T value=std::numeric_limits<T>::max()/2;
	static constexpr T mvalue=std::numeric_limits<T>::min()/2;
};
template<typename T>constexpr T INF=infinity<T>::value;
constexpr ll lINF=INF<ll>;
constexpr int iINF = INF<int>;
constexpr ld PI = 3.1415926535897932384626;

ll MOD = 998244353;

ll frac[4000001], inv[4000001];
ll MD = MOD;

ll fpow(ll x, ll y, ll mod) {
	if (!y) return 1%mod;
	x %= mod;
	ll ret = 1;
	while(y > 0) {
		if(y%2 == 1) ret = (ret*x)%mod;
		x = (x*x)%mod;
		y /= 2;
	}
	return ret;
}

void initComb() {
	frac[0] = 1;
	inv[0] = 1;
	for (int i = 1; i <= 4000000; i++) {
		frac[i] = (frac[i - 1] * i) % MD;
	}

	inv[4000000] = fpow(frac[4000000], MD - 2, MD);

	for (int i = 4000000; i > 0; i--) {
		inv[i - 1] = (inv[i] * i) % MD;
	}
}

ll C(ll n, ll k) {
	if (n < k)return 0;
	return ((frac[n] * inv[k]) % MD * inv[n - k]) % MD;
}

void _main() {
	initComb();
	// 불변량?
	ll N, M;
	cin >>N >>M;
	string S[N+1];
	for (ll i = 1; i<=N ; i++)cin>>S[i] , S[i] = " " + S[i];
	ll cntZAK = 0;
	ll cntHOL = 0;

	ll SUM1 = 0;// (짝수칸 - 홀수칸)
	ll SUM2 = 0;// (짝수칸 - 홀수칸)
	for (ll i = 1; i<=N; i++) {
		for (ll j=  1; j<=M; j++) {
			if (S[i][j] == '?') {
				if ((i+j)%2 == 0) {
					cntZAK ++;
				} else {
					cntHOL ++;
				}
			} else if ('B') {
				if ((i+j)%2 == 0) {
					SUM1 ++;// 짝
				} else {
					SUM2 ++;// 홀
				}
			}
		}
	}
	// SUM을 0으로 만들어야 함
	// 짝-홀을 SUM으로 만들어야 함
	ll RES = 0;
	for (ll zak = 0; zak<=cntZAK; zak++) {
		for (ll hol = 0; hol<=cntHOL; hol++) {
			if (abs(zak-SUM1)%2 == 0 && abs(hol-SUM2)%2 == 0) {
				RES += C(cntZAK, zak)*C(cntHOL, hol)%MOD;
				RES %= MOD;
			}
		}
	}
	cout << RES << endl;








}