using System;
using System.Text;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using static System.Console;
using static System.Math;

namespace C_test_For_Atcorder
{

    public static class Extensions
    {
        public static string Reverse(this string sourse){
            char[] chrAry = sourse.ToCharArray();
            Array.Reverse(chrAry);
            return new string(chrAry);
        }
    }

    public class Program
    {
        public static void Main(string[] args)
        {
            new Program().Solve(new ConsoleInput(Console.In, ' '));
        }


        public void Solve(ConsoleInput cin)
        {
            var ans = bfs(cin);
            Console.WriteLine(ans);
            return;
        }

        const int INF = -1;
		private int bfs(ConsoleInput cin)
		{
			var H = cin.ReadInt;
			var W = cin.ReadInt;
			var sy = 0;
			var sx = 0;
			var gy = H-1;
			var gx = W-1;
			var maze = new char[H,W];
			var d = new int[H, W];//各点までの最短距離の行列

            int countS = 0;

			for (int i = 0; i < H; i++)
			{
				var str = cin.Read;
                for (int j = 0; j < W; j++)
                {
                    maze[i, j] = str[j];
                    d[i, j] = INF;//初期化
                    //初期#の数を数える
                    if (str[j] == '#') countS++;
                }
			}
			var dy = new int[] { 0, 1, 0, -1 };
			var dx = new int[] { 1, 0, -1, 0 };

			//bfs
			var que = new Queue();
			que.Enqueue(new Tuple<int, int>(sy, sx));
			d[sy, sx] = 0;//初期地点設定

			while (que.Count > 0)
			{
				Tuple<int, int> p = que.Dequeue() as Tuple<int, int>;
				if (p.Item1 == gy && p.Item2 == gx) break;
				//移動四方向をループ
				for (int i = 0; i < 4; i++)
				{
					int ny = p.Item1 + dy[i];
					int nx = p.Item2 + dx[i];

					//移動判定
					if (0 <= ny && ny < H && 0 <= nx && nx < W && maze[ny, nx] != '#' && d[ny, nx] == INF)
					{
						que.Enqueue(new Tuple<int, int>(ny, nx));
						d[ny, nx] = d[p.Item1, p.Item2] + 1;
					}
				}
			}

            if(d[gy,gx]!=INF){
                return H * W - countS - d[gy, gx]-1;
            }
			return d[gy, gx];
		}

	}

    public class ConsoleInput
    {
        private readonly System.IO.TextReader _stream;
        private char _separator = ' ';
        private Queue inputStream;

        public ConsoleInput(System.IO.TextReader stream, char separator = ' ')
        {
            this._separator = separator;
            this._stream = stream;
            inputStream = new Queue();
        }
        public string Read
        {
            get
            {
                if (inputStream.Count != 0) return (string)inputStream.Dequeue();
                string[] tmp = _stream.ReadLine().Split(_separator);
                for (int i = 0; i < tmp.Length; ++i)
                    inputStream.Enqueue(tmp[i]);
                return (string)inputStream.Dequeue();
            }
        }
        public string ReadLine { get { return _stream.ReadLine(); } }
        public int ReadInt { get { return int.Parse(Read); } }
        public long ReadLong { get { return long.Parse(Read); } }
        public double ReadDouble { get { return double.Parse(Read); } }
        public string[] ReadStrArray(long N) { var ret = new string[N]; for (long i = 0; i < N; ++i) ret[i] = Read; return ret; }
        public int[] ReadIntArray(long N) { var ret = new int[N]; for (long i = 0; i < N; ++i) ret[i] = ReadInt; return ret; }
        public long[] ReadLongArray(long N) { var ret = new long[N]; for (long i = 0; i < N; ++i) ret[i] = ReadLong; return ret; }
    }

}


Measured memory_bytes: 13268