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

// macros
#define pb emplace_back
#define mk make_pair
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define whole(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define bit(n) (1LL<<(n))
// functions
template <typename T> void unique(T& c){c.erase(std::unique(c.begin(), c.end()), c.end());}
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << "(" << p.first << ", " << p.second << ")"; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
//  types
using ll = long long int;
using P = pair<int, int>;
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1000000007;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};
// io
struct fast_io{
  fast_io(){ios_base::sync_with_stdio(false); cin.tie(nullptr); cout << fixed << setprecision(20);}
} fast_io_;

template <typename T>
struct Graph {
  int n;
  vector<vector<pair<int, T> > > edge;
  vector<T> dis;
  Graph(int n): n(n) {
    edge.resize(n);
    dis.resize(n);
  }
  void dijkstra(int s){
    dijkstra(s, 0);
  }
  T dijkstra(int s, int t){
    // initialize
    fill(dis.begin(), dis.end(), -1);
    vector<bool> used(n, false);
    dis[s] = 0;
    // dijkstra
    priority_queue<pair<T, int>, vector<pair<T, int> >, greater<pair<T, int> > > q;
    q.push(make_pair(0, s));
    while(!q.empty()){
      pair<T, int> p = q.top(); q.pop();
      int at = p.second;
      T distance = p.first;
      if(used[at])continue;
      used[at] = true;
      for(auto itr = edge[at].begin(); itr != edge[at].end(); ++itr){
        int to = (*itr).first;
        T cost = (*itr).second;
        if(used[to])continue;
        if(dis[to] == -1 || dis[to] > distance + cost){
          q.push(make_pair(distance + cost, to));
          dis[to] = distance + cost;
        }
      }
    }
    return dis[t];
  }
  void adde(int at, int to, T cost){
    edge[at].push_back(make_pair(to, cost));
  }
  [[deprecated("This function takes O(|edge[at]|).")]]
  void remove(int at, int to){
    int index = -1;
    for(int i = 0; i < edge[at].size(); i++){
      if(edge[at][i].first == to){
        index = i;
        break;
      }
    }
    edge[at].erase(edge[at].begin() + index);
  }
};

using GraphI = Graph<int>;
using GraphL = Graph<ll>;
using GraphD = Graph<double>;

string s[51];

int main(int argc, char const* argv[])
{
  int h, w; cin >> h >> w;
  rep(i, h)cin >> s[i];
  GraphI g(h * w);
  rep(i, h){
    rep(j, w){
      if(s[i][j] == '#')continue;
      rep(k, 4){
        int nx = i + dx[k], ny = j + dy[k];
        if(nx >= 0 && nx < h && ny >= 0 && ny < w && s[nx][ny] != '#'){
          g.adde(i * w + j, nx * w + ny, 1);
        }
      }
    }
  }
  int b = 0;
  rep(i, h){
    rep(j, w){
      b += (s[i][j] == '#');
    }
  }
  int r = g.dijkstra(0, h * w - 1);
  if(r == -1)cout << -1 << endl;
  else cout << h * w - r - 1 - b << endl;
  return 0;
}


Measured memory_bytes: 512