//  Created by conan1024hao in 2019.
//  Copyright © 2019 conan1024hao. All rights reserved.
//  専用ライブラリです、自由にコピーして構いません。
//  感谢看我的代码！Wechat:conan1024hao Twitter/QQ:810396815
#pragma GCC optimize ("O3")
#include <iostream>
#include <iomanip>
#include <istream>
#include <ostream>
#include <sstream>
#include <iterator>
#include <vector>
#include <algorithm>
#include <queue>
#include <deque>
#include <list>
#include <stack>
#include <map>
#include <unordered_map>
#include <set>
#include <utility>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <string>
#include <ctime>
#include <cctype>
#include <cstdlib>
#define IINF 10e8
#define INF 10e16
#define MOD 1000000007
#define mod 1000000007
#define rep(i, a, n) for (ll i = a; i < (ll)(n); i++)
#define Endl endl
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define mmax(x,y)(x>y?x:y)
#define mmin(x,y)(x<y?x:y)
#define chmax(x,y) x=mmax(x,y)
#define chmin(x,y) x=mmin(x,y)
#define all(x) (x).begin(),(x).end()
#define siz(x) (ll)(x).size()
#define PI acos(-1.0)
using namespace std;
//using Int=int_fast64_t;
typedef long long int ll;
typedef pair<ll,ll>Pll;
typedef pair<int,int>Pin;
long long GCD(long long a, long long b) { return b ? GCD(b, a%b) : a; }
long long LCM(long long a, long long b)  {return a/GCD(a,b)*b;}
int dx[8]={-1,0,1,0,1,1,-1,-1};
int dy[8]={0,-1,0,1,1,-1,1,-1};
char dir[4]={'u','l','d','r'};
ll cmp1(pair<ll,string>a,pair<ll,string> b){
        if(a.fi!=b.fi)
        return a.fi<b.fi;
        else
        return a.se<b.se;
}
//---------------------------------------------------------------------------
bool color[60][60];int h,w;char s[200][100];int ans=0;
bool dfs(int x,int y){
    if(x==h-1&&y==w-1)
        return 1;
    if(color[x][y])return 0;
    color[x][y]=1;
    bool re=0;
    for(int i=0;i<4;i++){
        int nx=x+dx[i];
        int ny=y+dy[i];
        if(nx>=0&&ny>=0&&nx<h&&ny<w){
            if(color[nx][ny])
                continue;
            if(s[nx][ny]=='#')
                continue;
            re=dfs(nx,ny);
            if(re==1){
                return 1;
            }
        }
    }
    return 0;
}
//---------------------------------------------------------------------------
int main(){//問題をちゃんと見ろ!!!!!!!!!!!!!!!!!      llか??????????        memset()!!!!!!!!!!!!       ペナを減らせ!!!!!!!!!!!!!
    cin.tie(0);
    ios::sync_with_stdio(false);
    //-------------------------------
    cin>>h>>w;
    int white=0;
    for(int i=0;i<h;i++)
        for(int j=0;j<w;j++){
            cin>>s[i][j];
            if(s[i][j]=='.')
                white++;
        }
            
    white-=1;
    
    memset(color,0,sizeof(color));
    bool abc=dfs(0,0);
    if(abc==0){
        cout<<-1<<endl;
        return 0;
    }
    queue<Pin>Q;
    memset(color,0,sizeof(color));
    color[0][0]=1;
    int d[60][60];
    memset(d,0,sizeof(d));
    Q.push(mp(0,0));
    while(!Q.empty()){
        Pin p=Q.front();Q.pop();
        for(int i=0;i<4;i++){
        int nx=p.fi+dx[i];
        int ny=p.se+dy[i];
            if(nx>=0&&ny>=0&&nx<h&&ny<w){
                if(s[nx][ny]=='#')
                    continue;
                if(color[nx][ny])continue;
                else{
                    
                    color[nx][ny]=1;
                    d[nx][ny]=d[p.fi][p.se]+1;
                    if(nx==h-1&&ny==w-1){
                        cout<<white-d[nx][ny]<<endl;
                        return 0;
                    }
                    Q.push(mp(nx,ny));
                }
            }
        }
    }
    //-------------------------------
    return 0;
}
//---------------------------------------------------------------------------









Measured memory_bytes: 384