using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using static System.Console;
using static System.Math;
 
public class Solve{
    static public int mod = 1000000007;
    static public string al = "abcdefghijklmnopqrstuvwxyz";
    public static void Main(){
        // 方針
        //
        var tn = inta();
        var t = tn[0];
        var y = tn[1];
        var map = new char[t,y];
        
        var count = 0;
        for(int i=0;i<t;i++){
            var s = rstr();
            for(int j=0;j<y;j++){
                map[i,j] = s[j];
                if(map[i,j] == '.') count++;
            }
        }
        
        var queue = new Queue<int>();
        queue.Enqueue(0);
        queue.Enqueue(0);
        var countmap = new int[t,y];
        for(int i=0;i<t;i++){
            for(int j=0;j<y;j++){
                countmap[i,j] = 1000000001;
            }
        }
        countmap[0,0] = 1;
        var passed = new bool[t,y];
        
        var movet = new int[]{1,0,-1,0};
        var movey = new int[]{0,1,0,-1};
        while(queue.Count > 0){
            var det = queue.Dequeue();
            var dey = queue.Dequeue();
            if(passed[det,dey]) continue;
            passed[det,dey] = true;
            
            for(int i=0;i<4;i++){
                var nextt = det+ movet[i];
                var nexty = dey+ movey[i];
                if(!(0 <= nextt && nextt < t && 0 <= nexty && nexty < y)) continue;
                if(map[nextt,nexty] == '#') continue;
                countmap[nextt,nexty] = Min(countmap[nextt,nexty],countmap[det,dey]+1);
                queue.Enqueue(nextt);
                queue.Enqueue(nexty);
            }
        }
        if(countmap[t-1,y-1] > 1000000000){
            WriteLine(-1);
        }else{
            WriteLine(count - countmap[t-1,y-1]);
        }
        
	
	
    }
    public static void swap(ref int a,ref int b){int temp = a;a= b;b = temp;}
    static void charswap(ref char a,ref char b){char temp = a;a= b;b = temp;}
    static int ncr(int n,int r){if(n<r)return 0;r = Min(r,n-r);long nn = 1;for(int i=n-r+1;i<=n;i++){nn = nn*i%mod;}long rr = 1;for(int i=1;i<=r;i++){rr = rr*i%mod;}rr = square((int)rr,mod-2);nn = nn * rr %mod;return (int)nn;}
    // a^b mod
    static int square(int a,int b){string binary = Convert.ToString(b,2);int bileng = binary.Length;long a_power = a;long value = 1;for(int i=bileng-1;i>=0;i--){if(binary[i] == '1'){value = value*a_power%mod;}a_power = a_power*a_power%mod;}return (int)value;}
    static int square2(int a,int b){long output = 1;var list = new List<long>();int sh = 1;long n = a;list.Add(a);while(sh < b){sh *= 2;n = n*n%mod;list.Add(n);}for(int i=list.Count-1;i>=0;i--){if(b > sh){b -= sh;sh /= 2;output = output*list[i]%mod;}}return (int)output;}
    //各種読取
    static string rstr(){ return ReadLine(); }
    static int rint(){ return int.Parse(ReadLine()); }
    static long rlong(){ return long.Parse(ReadLine()); }
    static string[] stra(){ return ReadLine().Split(' '); }
    static char[] chara(){ string[] a=stra();string b="";for(int i=0;i<a.Length;i++){b+=a[i];}return b.ToCharArray();}
    static int[] inta(){ string[] read_str_array = ReadLine().Split(' '); int[] return_int_array = new int[read_str_array.Length]; for(int countup_i=0;countup_i<read_str_array.Length;countup_i++){ return_int_array[countup_i] = int.Parse(read_str_array[countup_i]); } return return_int_array; }
    static int[,] inta2(int num_array,int in_array){ int[,] int_array2 = new int[num_array,in_array]; for(int i=0;i<num_array;i++){ int[] temp_array = inta(); for(int j=0;j<in_array;j++){ int_array2[i,j] = temp_array[j]; } } return int_array2; }
    static long[] longa(){ string[] read_str_array = ReadLine().Split(' '); long[] return_long_array = new long[read_str_array.Length]; for(long countup_i=0;countup_i<read_str_array.Length;countup_i++){ return_long_array[countup_i] = long.Parse(read_str_array[countup_i]); } return return_long_array; }
    static double[] doublea(){ string[] read_str_array = ReadLine().Split(' '); double[] return_double_array = new double[read_str_array.Length]; for(long countup_i=0;countup_i<read_str_array.Length;countup_i++){ return_double_array[countup_i] = double.Parse(read_str_array[countup_i]); } return return_double_array; }
    // -----------------------------
    static long GCD(long a,long b){ if(a < b){ long temp = a; a = b; b = temp; } if(a % b == 0){ return b; } else{ long temp = b; b = a%b; a = temp; return GCD(a,b); } }
    static long LCM(long a,long b){ return a * b / GCD(a,b); }
    static void WriteArray(int[,] a,int b,int c){for(int i=0;i<b;i++){for(int j=0;j<c;j++){if(j!=0) Write(" ");Write(a[i,j]);}WriteLine();}}
}

Measured memory_bytes: 27848