#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
int main () {
	int N, M;
	cin >> N >> M;
	int now[] = {0, 0, 0};
	int cnt[] = {0, 0, 0};
	for (int i = 0; i < N; i ++) {
		for (int j = 0; j < M; j ++) {
			char c;
			cin >> c;
			if (c == '?') {
				cnt[(i + j)% 3] ++;
			} else {
				now[(i + j) % 3] ^= (c == 'B');
			}
		}
	}
	mint ans[3][2];
	for (int i = 0; i < 3; i ++) {
		if (cnt[i]) {
			ans[i][0] = ans[i][1] = ((mint)2).pow(cnt[i] - 1);
		} else {
			ans[i][now[i]] = 1;
			ans[i][now[i] ^ 1] = 0;
		}
	}
	mint r = 0;
	for (int j = 0; j < 2; j ++) {
		mint a = 1;
		for (int i = 0; i < 3; i ++) {
			a *= ans[i][j];
		}
		r += a;
	}
	cout << r.val() << endl;
}