#include <bits/stdc++.h>
#include <atcoder/modint>
using mint = atcoder::modint998244353;
using namespace std;
using ll = long long;

int main() {
    int n, m;
    cin >> n >> m;

    int b[3] = {}, q[3] = {};
    for (int i = 0; i < n; i++) {
        string s;
        cin >> s;
        for (int j = 0; j < m; j++) {
            int k = (i + j) % 3;
            b[k] ^= s[j] == 'B';
            q[k] += s[j] == '?';
        }
    }
    
    mint x = 0;
    for (int h = 0; h < 2; h++) {
        mint t = 1;
        for (int k = 0; k < 3; k++) {
            t *= q[k] ? mint(2).pow(q[k] - 1) : b[k] == h;
        }
        x += t;
    }
    cout << x.val() << endl;

    return 0;
}