using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
//using System.Text;
//using System.Text.RegularExpressions;
//using System.Globalization;
//using System.Diagnostics;
using static System.Console;
//using System.Numerics;
//using static System.Math;
using pair = Pair<int, int>;

class Program
{
    static void Main()
    {
        //SetOut(new StreamWriter(OpenStandardOutput()) { AutoFlush = false });
        new Program().solve();
        Out.Flush();
    }
    Scanner cin = new Scanner();
    readonly int[] dd = { 0, 1, 0, -1, 0 }; //→↓←↑
    readonly int mod = 1000000007;

    int H, W;
    void solve()
    {
        H = cin.nextint;
        W = cin.nextint;
        var C = new char[H][];
        int white = 0;
        for (int i = 0; i < H; i++)
        {
            C[i] = ReadLine().ToCharArray();
            white += C[i].Count(j => j == '.');
        }


        var Q = new Queue<pair>();
        Q.Enqueue(new pair(0, 0));
        var D = new int[H][];
        for (int i = 0; i < H; i++)
        {
            D[i] = Enumerable.Repeat(int.MaxValue, W).ToArray();
        }
        D[0][0] = 1;

        while (Q.Any())
        {
            var p = Q.Dequeue();
            if (p.f == H - 1 && p.s == W - 1)
            {
                continue;
            }
            for (int r = 0; r < 4; r++)
            {
                int y = p.f + dd[r];
                int x = p.s + dd[r + 1];
                if (y < 0 || y >= H || x < 0 || x >= W) continue;
                if (C[y][x] == '.' && D[p.f][p.s] + 1 < D[y][x])
                {
                    Q.Enqueue(new pair(y, x));
                    D[y][x] = D[p.f][p.s] + 1;
                }
            }
        }
        if (D[H - 1][W - 1] == int.MaxValue)
        {
            WriteLine(-1);
        }
        else
        {
            WriteLine(white - D[H - 1][W - 1]);
        }

    }

}

class Pair<T, U> : IComparable<Pair<T, U>> where T : IComparable<T> where U : IComparable<U>
{
    public T f;
    public U s;
    public Pair(T f, U s)
    {
        this.f = f;
        this.s = s;
    }
    public int CompareTo(Pair<T, U> a)
    {
        return f.CompareTo(a.f) != 0 ? f.CompareTo(a.f) : s.CompareTo(a.s);
    }
    public override string ToString()
    {
        return f + " " + s;
    }
}
class Scanner
{
    string[] s; int i;
    char[] cs = new char[] { ' ' };
    public Scanner() { s = new string[0]; i = 0; }
    public string[] scan { get { return ReadLine().Split(); } }
    public int[] scanint { get { return Array.ConvertAll(scan, int.Parse); } }
    public long[] scanlong { get { return Array.ConvertAll(scan, long.Parse); } }
    public double[] scandouble { get { return Array.ConvertAll(scan, double.Parse); } }
    public string next
    {
        get
        {
            if (i < s.Length) return s[i++];
            string st = ReadLine();
            while (st == "") st = ReadLine();
            s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            i = 0;
            return next;
        }
    }
    public int nextint { get { return int.Parse(next); } }
    public long nextlong { get { return long.Parse(next); } }
    public double nextdouble { get { return double.Parse(next); } }
}

Measured memory_bytes: 13652