#include<stdio.h>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <queue> 
 
using namespace std;
 
//conversion
//------------------------------------------
inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}
 
//math
//-------------------------------------------
template<class T> inline T sqr(T x) {return x*x;}
 
//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
 
//container util
//------------------------------------------
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
 
//repetition
//------------------------------------------
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)
 
//constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI  = acos(-1.0);
 
//clear memory
#define CLR(a) memset((a), 0 ,sizeof(a))
 
//debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

//pair sort
bool compare_by_b(pair<LL, LL> a, pair<LL, LL> b) {
    if(a.second != b.second){
        return a.second < b.second;
    }else{
        return a.first < b.first;
    }
}

int sx,sy,gx,gy;
char m[52][52];
int dist[52][52];
int r,c;
int dx[4] ={0,1,0,-1};
int dy[4] ={1,0,-1,0};

typedef pair<int, int> P;

int bfs(){
    P sp = make_pair(sy,sx);
    queue<P> que;
    que.push(sp);
    dist[sy][sx]=0;
    int d=0;
    while(!que.empty()){
        P poi = que.front();
        que.pop();
        if(poi.first==gy && poi.second==gx){
            break;
        }
        for(int i=0; i < 4; i++){
            P pon = make_pair(poi.first+dy[i], poi.second+dx[i]);
            if(dist[pon.first][pon.second]==10000 &&
            pon.first>0 && pon.first<=r &&
            pon.second>0 && pon.second<=c
            && m[pon.first][pon.second]=='.'){
                dist[pon.first][pon.second] = dist[poi.first][poi.second]+1;
                que.push(pon);
            }
        }
    }
}

int main(){
    // Failed to predict input format

    cin>>r>>c;
    sx=sy=1;
    gy=r;gx=c;
    int whites=0;
    REP(i,r){
        REP(j,c){
            cin>>m[i+1][j+1];
            if(m[i+1][j+1]=='.')whites++;
        }
    }
    REP(i,52)REP(j,52)dist[i][j]=10000;
    bfs();
    if(dist[gy][gx]==10000){
        cout<<-1<<endl;return 0;
    }
    cout<<whites-dist[gy][gx]-1<<endl;
    return 0;
}


Measured memory_bytes: 256