using System;
using System.Collections.Generic;
using System.Linq;
using BitArray = System.Collections.BitArray;
using BigInteger = System.Numerics.BigInteger;
using TextReader = System.IO.TextReader;
using System.Text;

namespace AtCoderProject
{
    public class Program
    {
        public object Calc()
        {
            var H = consoleReader.Int;
            var W = consoleReader.Int;
            var blocks = new bool[W, H];
            var sumi = new bool[W, H];
            sumi[0, 0] = true;
            var count = 1;
            var current = new List<Point> { new Point() };
            var goal = new Point { h = H - 1, w = W - 1 };
            var all = 0;
            for (int h = 0; h < H; h++)
            {
                var line = consoleReader.String;
                for (int w = 0; w < W; w++)
                {
                    if (line[w] == '.')
                    {
                        blocks[w, h] = true;
                        all++;
                    }
                }
            }

            while (true)
            {
                ++count;
                var next = new List<Point>();
                foreach (var c in current)
                {
                    if (c.w > 0 && blocks[c.w - 1, c.h] && !sumi[c.w - 1, c.h])
                    {
                        var p = new Point(c.w - 1, c.h);
                        sumi[c.w - 1, c.h] = true;
                        next.Add(p);
                    }
                    if (c.w < W - 1 && blocks[c.w + 1, c.h] && !sumi[c.w + 1, c.h])
                    {
                        var p = new Point(c.w + 1, c.h);
                        sumi[c.w + 1, c.h] = true;
                        if (p.Equals(goal))
                            return all - count;
                        next.Add(p);
                    }
                    if (c.h > 0 && blocks[c.w, c.h - 1] && !sumi[c.w, c.h - 1])
                    {
                        var p = new Point(c.w, c.h - 1);
                        sumi[c.w, c.h - 1] = true;
                        next.Add(p);
                    }
                    if (c.h < H - 1 && blocks[c.w, c.h + 1] && !sumi[c.w, c.h + 1])
                    {
                        var p = new Point(c.w, c.h + 1);
                        if (p.Equals(goal))
                            return all - count;
                        sumi[c.w, c.h + 1] = true;
                        next.Add(p);
                    }
                }
                if (next.Count == 0)
                    return -1;
                current = next;
            }
        }

        struct Point : IEquatable<Point>
        {
            public int w;
            public int h;
            public Point(int x, int y)
            {
                this.w = x;
                this.h = y;
            }
            public bool Equals(Point other) => this.w == other.w && this.h == other.h;
            public override bool Equals(object obj)
            {
                if (obj is Point) return Equals((Point)obj);
                return false;
            }
            public override int GetHashCode() => w << 16 | h;
            public override string ToString() => $"({w}, {h})";
        }

        #region いつもの
#pragma warning disable
        private ConsoleReader consoleReader;
        public Program(ConsoleReader consoleReader) { this.consoleReader = consoleReader; }
        static void Main() => Console.WriteLine(new Program(new ConsoleReader(Console.In)).Calc()); static string AllLines<T>(IEnumerable<T> source) => string.Join("\n", source);
    }
    public class ConsoleReader
    {
        private string[] ReadLineSplit() => textReader.ReadLine().Split(Array.Empty<char>(), StringSplitOptions.RemoveEmptyEntries);
        private string[] line = Array.Empty<string>();
        private int linePosition;
        private TextReader textReader;
        public ConsoleReader(TextReader tr) { textReader = tr; }
        public int Int => int.Parse(String);
        public long Long => long.Parse(String);
        public double Double => double.Parse(String);
        public string String
        {
            get
            {
                if (linePosition >= line.Length)
                {
                    linePosition = 0;
                    line = ReadLineSplit();
                }
                return line[linePosition++];
            }
        }
        public class SplitLine
        {
            private string[] splited;
            public SplitLine(ConsoleReader cr) { splited = cr.ReadLineSplit(); cr.line = Array.Empty<string>(); }
            public int[] Int => String.Select(x => int.Parse(x)).ToArray();
            public int[] Int0 => String.Select(x => int.Parse(x) - 1).ToArray();
            public long[] Long => String.Select(x => long.Parse(x)).ToArray();
            public double[] Double => String.Select(x => double.Parse(x)).ToArray();
            public string[] String => splited;
        }
        public SplitLine Split => new SplitLine(this);
        public class RepeatReader : IEnumerable<ConsoleReader>
        {
            ConsoleReader cr; int count;
            public RepeatReader(ConsoleReader cr, int count) { this.cr = cr; this.count = count; }
            public IEnumerator<ConsoleReader> GetEnumerator() => Enumerable.Repeat(cr, count).GetEnumerator();
            System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() => GetEnumerator();

            public IEnumerable<string> String => this.Select(cr => cr.String);
            public IEnumerable<int> Int => this.Select(cr => cr.Int);
            public IEnumerable<int> Int0 => this.Select(cr => cr.Int - 1);
            public IEnumerable<long> Long => this.Select(cr => cr.Long);
            public IEnumerable<double> Double => this.Select(cr => cr.Double);
        }
        public RepeatReader Repeat(int count) => new RepeatReader(this, count);
    }
    #endregion
}

Measured memory_bytes: 13396