using namespace std;
#include <iostream>
#include <bits/stdc++.h>

#define infile "../test/sample-1.in"
#define int long long
// #define INF 2147483647
#define INF 1000000000000000000LL
#define MOD 1000000007LL

// {{{ define basic macro
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(int i=(int)(a);i<(int)(b);++i)
#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define _rrep(i,n) repi(i,0,n)
#define rrepi(i,a,b) for(int i=(int)(b-1);i>=(int)(a);--i)
#define rrep(...) _overload3(__VA_ARGS__,rrepi,_rrep,)(__VA_ARGS__)

#define foreach(x,a) for(auto& (x) : (a) )
#define each(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)

#define all(x) (x).begin(),(x).end()
#define sum(v) accumulate(all(v), 0)
#define sz(x) ((int)(x).size())
template<class T> inline void chmax(T &a, const T &b) { if(a < b) a = b; }
template<class T> inline void chmin(T &a, const T &b) { if(a > b) a = b; }
// n次元配列の初期化。第２引数の型のサイズごとに初期化していく。
template<typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val){
    std::fill( (T*)array, (T*)(array+N), val );
}
#define fill(x,y) memset(x,y,sizeof(x))
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define uni(x) sort(all(x));x.erase(unique(all(x)),x.end())
#define ten(n) ((int)1e##n)

template <class T = int>
T in() {T x; cin>>x; return (x);}

struct Fast {
  Fast(){
    std::cin.tie(0);
    ios::sync_with_stdio(false);
  }
} fast;
// }}}
//{{{ dump macro
#ifdef PCM
  #include "dump.hpp"
#else
  #define dump(...) 42
  #define dump_1d(...) 42
  #define dump_2d(...) 42
#endif
//}}}
//{{{ others
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef long double ld;
typedef pair<int,int> pii;
typedef tuple<int,int,int> iii;
template<typename T>
using PQ = priority_queue<T, vector<T>, greater<T>>;

int dx[]={1, -1, 0, 0};
int dy[]={0, 0, 1, -1};
//}}}

//{{{ dijkstra(start, graph, inf_for_initing_cost)
template <typename cost, typename node>
vector<cost> dijkstra(
    // return d (d[i]:iへの最短距離)
    node s, //start node
    vector<vector<pair<node, cost>>> & G,  //Graph
    cost inf // cost初期化用の十分大きな値
    ){
  using P = pair<cost, node>; // <cost, v> costをkeyにするため
  node n=G.size();
  vector<cost> d(n, inf);  // 最短距離
  priority_queue<P, vector<P>, greater<P>> q;

  d[s]=0; q.emplace(d[s], s);
  while(!q.empty()){
    P p=q.top();q.pop();
    node v=p.second;
    if(d[v]<p.first) continue;
    for(auto& e:G[v]){
      node u=e.first;
      cost c=e.second;
      if(d[u]>d[v]+c){
        d[u]=d[v]+c;
        q.emplace(d[u],u);
      }
    }
  }
  return d;
} //}}}

int M[50][50];
int d[50][50];
int solve(){
  int h,w;cin>>h>>w;
  int bcnt = 0;
  rep(i, h) rep(j, w){
    char c;cin>>c;
    M[i][j] = c;
    if (c=='#') bcnt++;
  }

  rep(i, 50) rep(j, 50){ d[i][j]=INF; }  // dの初期化
  auto s = mp(0,0);  // startの設定
  typedef pair<int, pii> CP;  // (cost, pos)
  PQ<CP> q;
  q.push(CP(0LL, pii(s.first, s.second)));
  while (!q.empty()){
    auto v = q.top(); q.pop();
    int cost = v.first;
    int x = v.second.first;
    int y = v.second.second;
    if (cost < d[x][y]){
      d[x][y] = cost;
      rep(i, 4){
        int nx = x+dx[i];
        int ny = y+dy[i];
        if (0<= nx && nx <= h-1 && 0<=ny && ny <= w-1){
          if (M[nx][ny]=='.') q.push(mp(cost+1, mp(nx, ny)));
        }
      }
    }
  }
  dump_2d(d, h, w);

  if (d[h-1][w-1]==INF) {
    cout << -1 << endl;
    return 0;
  }

  cout << (h*w)-d[h-1][w-1]-1-bcnt << endl;

  return 0;
}

int test(){ //{{{
  return 0;
}
//}}}

signed main() { //{{{
#ifdef INPUT_FROM_FILE
  std::ifstream in(infile);
  std::cin.rdbuf(in.rdbuf());
#endif
#ifdef PCM
  test();
#endif
  solve();
  return 0;
} //}}}


Measured memory_bytes: 256