#include <bits/stdc++.h>
#ifdef LOCAL
#include <debug.hpp>
#else
#define debug(...) void(0)
#endif

template <class T> std::istream& operator>>(std::istream& is, std::vector<T>& v) {
    for (auto& e : v) {
        is >> e;
    }
    return is;
}

template <class T> std::ostream& operator<<(std::ostream& os, const std::vector<T>& v) {
    for (std::string_view sep = ""; const auto& e : v) {
        os << std::exchange(sep, " ") << e;
    }
    return os;
}

template <class T, class U = T> bool chmin(T& x, U&& y) {
    return y < x and (x = std::forward<U>(y), true);
}

template <class T, class U = T> bool chmax(T& x, U&& y) {
    return x < y and (x = std::forward<U>(y), true);
}

template <class T> void mkuni(std::vector<T>& v) {
    std::ranges::sort(v);
    auto result = std::ranges::unique(v);
    v.erase(result.begin(), result.end());
}

template <class T> int lwb(const std::vector<T>& v, const T& x) {
    return std::distance(v.begin(), std::ranges::lower_bound(v, x));
}

#include <atcoder/modint>

template <typename T> struct Binomial {
    Binomial(int MAX = 0) : n(1), facs(1, T(1)), finvs(1, T(1)), invs(1, T(1)) {
        assert(T::mod() != 0);
        if (MAX > 0) extend(MAX + 1);
    }

    T fac(int i) {
        assert(i >= 0);
        while (n <= i) extend();
        return facs[i];
    }

    T finv(int i) {
        assert(i >= 0);
        while (n <= i) extend();
        return finvs[i];
    }

    T inv(int i) {
        assert(i >= 0);
        while (n <= i) extend();
        return invs[i];
    }

    T P(int n, int r) {
        if (n < 0 || n < r || r < 0) return T(0);
        return fac(n) * finv(n - r);
    }

    T C(int n, int r) {
        if (n < 0 || n < r || r < 0) return T(0);
        return fac(n) * finv(n - r) * finv(r);
    }

    T H(int n, int r) {
        if (n < 0 || r < 0) return T(0);
        return r == 0 ? 1 : C(n + r - 1, r);
    }

    T C_naive(int n, int r) {
        if (n < 0 || n < r || r < 0) return T(0);
        T res = 1;
        r = std::min(r, n - r);
        for (int i = 1; i <= r; i++) res *= inv(i) * (n--);
        return res;
    }

  private:
    int n;
    std::vector<T> facs, finvs, invs;

    inline void extend(int m = -1) {
        if (m == -1) m = n * 2;
        m = std::min(m, T::mod());
        if (n >= m) return;
        facs.resize(m);
        finvs.resize(m);
        invs.resize(m);
        for (int i = n; i < m; i++) facs[i] = facs[i - 1] * i;
        finvs[m - 1] = T(1) / facs[m - 1];
        invs[m - 1] = finvs[m - 1] * facs[m - 2];
        for (int i = m - 2; i >= n; i--) {
            finvs[i] = finvs[i + 1] * (i + 1);
            invs[i] = finvs[i] * facs[i - 1];
        }
        n = m;
    }
};

using ll = long long;

using namespace std;

using mint = atcoder::modint998244353;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);
    Binomial<mint> BINOM;
    int N, M;
    cin >> N >> M;
    vector<string> S(N);
    cin >> S;

    vector dp(2, vector(2, vector<mint>(2, 0))), ndp(2, vector(2, vector<mint>(2, 0)));
    dp[0][0][0] = 1;
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < M; j++) {
            char c = S[i][j];
            int k = (i + j) % 3;
            for (int p = 0; p < 2; p++) {
                for (int q = 0; q < 2; q++) {
                    for (int r = 0; r < 2; r++) {
                        mint& val = dp[p][q][r];
                        if (val == 0) continue;
                        if (k == 0) {
                            if (c != 'W') ndp[p ^ 1][q][r] += val;
                            if (c != 'B') ndp[p][q][r] += val;
                        } else if (k == 1) {
                            if (c != 'W') ndp[p][q ^ 1][r] += val;
                            if (c != 'B') ndp[p][q][r] += val;
                        } else {
                            if (c != 'W') ndp[p][q][r ^ 1] += val;
                            if (c != 'B') ndp[p][q][r] += val;
                        }
                        val = 0;
                    }
                }
            }
            swap(dp, ndp);
        }
    }
    mint ans = dp[0][0][0] + dp[1][1][1];

    cout << ans.val() << "\n";
    return 0;
}