namespace AtCoder;

#nullable enable

using System.Numerics;

static class Extensions
{
    public static T[] Repeat<T>(this int time, Func<T> F) => Enumerable.Range(0, time).Select(_ => F()).ToArray();
}

readonly record struct ModInt :
    IEqualityOperators<ModInt, ModInt, bool>,
    IAdditiveIdentity<ModInt, ModInt>,
    IAdditionOperators<ModInt, ModInt, ModInt>,
    IUnaryNegationOperators<ModInt, ModInt>,
    ISubtractionOperators<ModInt, ModInt, ModInt>,
    IMultiplicativeIdentity<ModInt, ModInt>,
    IMultiplyOperators<ModInt, ModInt, ModInt>,
    IDivisionOperators<ModInt, ModInt, ModInt>
{
    int V { get; init; }
    public const int Mod = 998244353;
    public ModInt(long value)
    {
        var v = value % Mod;
        if (v < 0) v += Mod;
        V = (int)v;
    }
    ModInt(int value) { V = value; }

    public static implicit operator ModInt(long v) => new(v);
    public static implicit operator int(ModInt modInt) => modInt.V;
    public static ModInt operator +(ModInt a, ModInt b)
    {
        var v = a.V + b.V;
        if (v >= Mod) v -= Mod;
        return new(v);
    }
    public static ModInt operator -(ModInt a) => new(a.V == 0 ? 0 : Mod - a.V);
    public static ModInt operator -(ModInt a, ModInt b)
    {
        var v = a.V - b.V;
        if (v < 0) v += Mod;
        return new(v);
    }
    public static ModInt operator *(ModInt a, ModInt b) => new((int)((long)a.V * b.V % Mod));
    public static ModInt operator /(ModInt a, ModInt b)
    {
        if (b == 0) throw new DivideByZeroException();
        var (d, x, _) = ExtendedGcd(b.V, Mod);
        if (d > 1) throw new DivideByZeroException();
        return x * a.V;
    }

    public ModInt Power(long p)
    {
        if (p < 0) return (MultiplicativeIdentity / V).Power(-p);
        long res = 1;
        long k = V;
        while (p > 0)
        {
            if ((p & 1) > 0) res = res * k % Mod;
            k = k * k % Mod;
            p >>= 1;
        }
        return res;
    }

    static (long d, long x, long y) ExtendedGcd(long a, long b)
    {
        if (b == 0) return (a, 1, 0);
        var (d, x, y) = ExtendedGcd(b, a % b);
        return (d, y, x - a / b * y);
    }

    public static ModInt AdditiveIdentity => new(0);
    public static ModInt MultiplicativeIdentity => new(1);

    public override string ToString() => V.ToString();
}

class AtCoder
{
    object? Solve()
    {
        var n = Int();
        var m = Int();
        var sz = n.Repeat(String);

        var dpz = new ModInt[n][];
        for (var i = 0; i < n; i++)
        {
            var siz = sz[i].AsSpan();
            var dp = new ModInt[8];
            dp[0] = 1;
            for (var j = 0; j < m; j++)
            {
                var ep = new ModInt[8];
                var c = siz[j];
                if (c != 'W') for (var k = 0; k < 4; k++) ep[(k << 1) | 1] += dp[k];
                if (c != 'B') for (var k = 0; k < 4; k++) ep[k << 1] += dp[k];
                for (var k = 4; k < 8; k++)
                {
                    ep[k ^ 7] += ep[k];
                    ep[k] = 0;
                }
                dp = ep;
            }
            dpz[i] = dp;
        }
        var fp = new ModInt[8, 8];
        fp[0, 0] = 1;
        for (var i = 0; i < n; i++)
        {
            var dp = dpz[i];
            var gp = new ModInt[8, 8];
            for (var x = 0; x < 4; x++) for (var y = 0; y < 4; y++)
            {
                var v = fp[x, y];
                for (var k = 0; k < 4; k++)
                {
                    var p = k >> 1;
                    var q = k & 1;
                    gp[(x << 1) | p, (y << 1) | q] += v * dp[k];
                }
            }
            for (var x = 4; x < 8; x++) for (var y = 0; y < 4; y++)
            {
                gp[x ^ 7, y] += gp[x, y];
                gp[x, y] = 0;
            }
            for (var x = 0; x < 4; x++) for (var y = 4; y < 8; y++)
            {
                gp[x, y ^ 7] += gp[x, y];
                gp[x, y] = 0;
            }
            for (var x = 4; x < 8; x++) for (var y = 4; y < 8; y++)
            {
                gp[x ^ 7, y ^ 7] += gp[x, y];
                gp[x, y] = 0;
            }
            fp = gp;
        }
        var ans = fp[0, 0] + fp[1, 2] + fp[3, 1] + fp[2, 3];
        return ans;
    }

    public static void Main() => new AtCoder().Run();
    public void Run()
    {
        var res = Solve();
        if (res != null)
        {
            if (res is bool yes) res = yes ? "Yes" : "No";
            sw.WriteLine(res);
        }
        sw.Flush();
    }

    string[] input = Array.Empty<string>();
    int iter = 0;
    readonly StreamWriter sw = new(Console.OpenStandardOutput()) { AutoFlush = false };

    string String()
    {
        while (iter >= input.Length) (input, iter) = (Console.ReadLine()!.Split(' '), 0);
        return input[iter++];
    }
    T Input<T>() where T : IParsable<T> => T.Parse(String(), null);
    int Int() => Input<int>();
    void Out(object? x, string? separator = null)
    {
        separator ??= Environment.NewLine;
        if (x is System.Collections.IEnumerable obj and not string)
        {
            var firstLine = true;
            foreach (var item in obj)
            {
                if (!firstLine) sw.Write(separator);
                firstLine = false;
                sw.Write(item);
            }
        }
        else sw.Write(x);
        sw.WriteLine();
    }
}