using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var H = sc.ReadInt();
        var W = sc.ReadInt();
        var A = sc.ReadStrArray(H);
        var v = new int[H, W];
        var wCount = A.Sum(a => a.Count(c => c == '.'));
        var q = new Queue<Tuple<int, int, int>>();
        q.Enqueue(Tuple.Create(0, 0, 0));
        v[0, 0] = 0;
        for (int i = 0; i < H; i++)
        {
            for (int j = 0; j < W; j++)
            {
                v[i, j] = -1;
            }
        }
        var max = 0;
        while (q.Count > 0)
        {
            var xy = q.Dequeue();
            var x = xy.Item1;
            var y = xy.Item2;
            var cost = xy.Item3;
            if (A[y][x] == '#') continue;
            else v[y, x] = cost;
            if (x > 0 && v[y, x - 1] < 0)
            {
                v[y, x - 1] = cost + 1;
                q.Enqueue(Tuple.Create(x - 1, y, cost + 1));
            }
            if (x < W - 1 && v[y, x + 1] < 0)
            {
                v[y, x + 1] = cost + 1;
                q.Enqueue(Tuple.Create(x + 1, y, cost + 1));
            }
            if (y > 0 && v[y - 1, x] < 0)
            {
                v[y - 1, x] = cost + 1;
                q.Enqueue(Tuple.Create(x, y - 1, cost + 1));
            }
            if (y < H - 1 && v[y + 1, x] < 0)
            {
                v[y + 1, x] = cost + 1;
                q.Enqueue(Tuple.Create(x, y + 1, cost + 1));
            }
            if (x == W - 1 && y == H - 1)
            {
                max = cost;
                break;
            }
        }
        if (v[H - 1, W - 1] < 0)
        {
            Console.WriteLine(-1);
            return;
        }
        var ans = wCount - max - 1;
        Console.WriteLine(ans);
    }
    static Scanner sc = new Scanner();
}

class Scanner
{
    string[] S = new string[0];
    int Index = 0;
    char[] Separators = new char[] { ' ' };

    public string Next()
    {
        if (this.Index < this.S.Length) return this.S[this.Index++];
        var line = "";
        while (line == "") line = Console.ReadLine();
        this.S = line.Split(this.Separators, StringSplitOptions.RemoveEmptyEntries);
        if (this.S.Length == 0) return this.Next();
        this.Index = 0;
        return this.S[this.Index++];
    }
    public string ReadStr()
    {
        return this.Next();
    }
    public char ReadChar()
    {
        return this.Next()[0];
    }
    public int ReadInt()
    {
        return int.Parse(this.Next());
    }
    public uint ReadUInt()
    {
        return uint.Parse(this.Next());
    }
    public long ReadLong()
    {
        return long.Parse(this.Next());
    }
    public double ReadDouble()
    {
        return double.Parse(this.Next());
    }
    public Tuple<int, int> ReadTup()
    {
        return Tuple.Create(this.ReadInt(), this.ReadInt());
    }
    public Tuple<long, long> ReadTupLong()
    {
        return Tuple.Create(this.ReadLong(), this.ReadLong());
    }
    public Tuple<int, int, int> ReadTup3()
    {
        return Tuple.Create(this.ReadInt(), this.ReadInt(), this.ReadInt());
    }
    public Tuple<int, int, int, int> ReadTup4()
    {
        return Tuple.Create(this.ReadInt(), this.ReadInt(), this.ReadInt(), this.ReadInt());
    }
    public int[] ReadIntArray(int n)
    {
        var array = new int[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadInt();
        }
        return array;
    }
    public long[] ReadLongArray(int n)
    {
        var array = new long[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadLong();
        }
        return array;
    }
    public double[] ReadDoubleArray(int n)
    {
        var array = new double[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadDouble();
        }
        return array;
    }
    public char[] ReadCharArray(int n)
    {
        var array = new char[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadChar();
        }
        return array;
    }
    public string[] ReadStrArray(int n)
    {
        var array = new string[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadStr();
        }
        return array;
    }
    public Tuple<long, long>[] ReadTupLongArray(int n)
    {
        var array = new Tuple<long, long>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTupLong();
        }
        return array;
    }
    public Tuple<int, int>[] ReadTupArray(int n)
    {
        var array = new Tuple<int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup();
        }
        return array;
    }
    public Tuple<int, int, int>[] ReadTup3Array(int n)
    {
        var array = new Tuple<int, int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup3();
        }
        return array;
    }
    public Tuple<int, int, int, int>[] ReadTup4Array(int n)
    {
        var array = new Tuple<int, int, int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup4();
        }
        return array;
    }
}


Measured memory_bytes: 13524