using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using Enu = System.Linq.Enumerable;

class Program
{
    static readonly int[] DR = { 0, -1, 0, 1 };
    static readonly int[] DC = { 1, 0, -1, 0 };
    static readonly int[] MoveCand = { 0, 1, 3 };
    int H, W, EmptyCount;
    string[] grid;

    void Solve()
    {
        H = reader.Int();
        W = reader.Int();
        grid = reader.StringArray(H);
        EmptyCount = string.Join("", grid).Count(c => c == '.');
        int first = Enu.Range(0, H * W).First(i => grid[i / W][i % W] == '.');
        bool ok = Enu.Range(0, 4).Any(d => OK(first / W, first % W, d));
        Console.WriteLine(ok ? "YES" : "NO");
    }

    private bool OK(int sr, int sc, int d)
    {
        var seen = new bool[grid.Length, grid[0].Length];
        int count = 0, moveR = 0, r = sr, c = sc;
        while (true)
        {
            if (!MoveNext(ref r, ref c, ref d, ref moveR, seen)) break;
            count++;
            seen[r, c] = true;
        }
        return count == EmptyCount && moveR <= 1;
    }
    bool MoveNext(ref int r, ref int c, ref  int d, ref int R, bool[,] seen)
    {
        for (int move = 0; move < MoveCand.Length; move++)
        {
            int nd = (d + move) % DR.Length;
            int nr = r + DR[nd], nc = c + DC[nd];
            if (Movable(nr, nc) && !seen[nr, nc]) { r = nr; c = nc; d = nd; if (move == 2) R++; return true; }
        }
        return false;
    }
    bool Movable(int r, int c) { return r >= 0 && r < H && c >= 0 && c < W && grid[r][c] == '.'; }




    Reader reader = new Reader(Console.In);
    static void Main() { new Program().Solve(); }
}

class Reader
{
    private readonly TextReader reader;
    private readonly char[] separator = { ' ' };
    private readonly StringSplitOptions removeOp = StringSplitOptions.RemoveEmptyEntries;
    private string[] A = new string[0];
    private int i;

    public Reader(TextReader r) { reader = r; }
    public Reader(string file) { reader = new StreamReader(file); }
    public bool HasNext() { return Enqueue(); }
    public string String() { return Dequeue(); }
    public int Int() { return int.Parse(Dequeue()); }
    public long Long() { return long.Parse(Dequeue()); }
    public double Double() { return double.Parse(Dequeue()); }
    public int[] IntLine() { var s = Line(); return s == "" ? new int[0] : Array.ConvertAll(Split(s), int.Parse); }
    public int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); }
    public int[][] IntGrid(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); }
    public string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Line()).ToArray(); }
    public string Line() { return reader.ReadLine().Trim(); }
    private string[] Split(string s) { return s.Split(separator, removeOp); }
    private bool Enqueue()
    {
        if (i < A.Length) return true;
        string line = reader.ReadLine();
        if (line == null) return false;
        if (line == "") return Enqueue();
        A = Split(line);
        i = 0;
        return true;
    }
    private string Dequeue() { Enqueue(); return A[i++]; }
}