using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

namespace AtCorder
{
	public class Program
	{
		static void Main(string[] args)
		{
			var cin = new Scanner2();
			int h = cin.Int();
			int w = cin.Int();
			var s = new string[h];
			for (int i = 0; i < h; i++) {
				s[i] = cin.Next();
			}

			var d = new DXY[h, w];
			for (int i = 0; i < h; i++) {
				for (int j = 0; j < w; j++) {
					d[i, j] = new DXY { D = int.MaxValue, PX = -1, PY = -1 };
				}
			}

			d[0, 0] = new DXY { D = 0, PX = -1, PY = -1 };
			var q = new Queue<Tuple<int, int>>();
			q.Enqueue(new Tuple<int, int>(0, 0));
			int[] delta = { 1, 0, -1, 0, 1 };
			while (q.Count > 0) {
				var cur = q.Dequeue();
				int i = cur.Item1;
				int j = cur.Item2;
				for (int n = 0; n < 4; n++) {
					int ii = i + delta[n];
					int jj = j + delta[n + 1];
					if (ii >= 0 && jj >= 0 && ii < h && jj < w) {
						if (s[ii][jj] == '#') {
							continue;
						}

						if (d[ii, jj].D > d[i, j].D + 1) {
							d[ii, jj] = new DXY { D = d[i, j].D + 1, PY = i, PX = j };
							q.Enqueue(new Tuple<int, int>(ii, jj));
						}
					}
				}
			}

			if (d[h - 1, w - 1].D == int.MaxValue) {
				Console.WriteLine(-1);
				return;
			}

			var root = new bool[h, w];
			root[0, 0] = true;
			root[h - 1, w - 1] = true;
			int nx = d[h - 1, w - 1].PX;
			int ny = d[h - 1, w - 1].PY;
			while (nx >= 0 && ny >= 0) {
				root[ny, nx] = true;
				int nnx = d[ny, nx].PX;
				int nny = d[ny, nx].PY;
				nx = nnx;
				ny = nny;
			}

			int ans = 0;
			for (int i = 0; i < h; i++) {
				for (int j = 0; j < w; j++) {
					if (s[i][j] == '.' && root[i, j] == false) {
						++ans;
					}
				}
			}

			Console.WriteLine(ans);
		}

		struct DXY
		{
			public int D { get; set; }
			public int PX { get; set; }
			public int PY { get; set; }
		}
	}

	public class Scanner2
	{
		private readonly char[] delimiter_ = new char[] { ' ' };
		private readonly string filePath_;
		private readonly Func<string> reader_;
		private string[] buf_;
		private int index_;

		public Scanner2(string file = "")
		{
			if (string.IsNullOrWhiteSpace(file)) {
				reader_ = Console.ReadLine;
			} else {
				filePath_ = file;
				var fs = new StreamReader(file);
				reader_ = fs.ReadLine;
			}
			buf_ = new string[0];
			index_ = 0;
		}

		public string Next()
		{
			if (index_ < buf_.Length) {
				return buf_[index_++];
			}

			string st = reader_();
			while (st == "") {
				st = reader_();
			}

			buf_ = st.Split(delimiter_, StringSplitOptions.RemoveEmptyEntries);
			if (buf_.Length == 0) {
				return Next();
			}

			index_ = 0;
			return buf_[index_++];
		}

		public int Int() => int.Parse(Next());
		public long Long() => long.Parse(Next());
		public double Double() => double.Parse(Next());

		public int[] ArrayInt(int N, int add = 0)
		{
			int[] Array = new int[N];
			for (int i = 0; i < N; i++) {
				Array[i] = Int() + add;
			}
			return Array;
		}

		public long[] ArrayLong(int N, long add = 0)
		{
			long[] Array = new long[N];
			for (int i = 0; i < N; i++) {
				Array[i] = Long() + add;
			}
			return Array;
		}

		public double[] ArrayDouble(int N, double add = 0)
		{
			double[] Array = new double[N];
			for (int i = 0; i < N; i++) {
				Array[i] = Double() + add;
			}
			return Array;
		}

		public void Save(string text)
		{
			if (string.IsNullOrWhiteSpace(filePath_)) {
				return;
			}

			File.WriteAllText(filePath_ + "_output.txt", text);
		}
	}
}

Measured memory_bytes: 11348