#include <iostream>
#include <list>
#include <set>
#include <queue>
#include <stack>
#include <vector>
#include <algorithm>
#include <map>
#include <chrono>
#include <math.h>
using namespace std;

using lli = long long int;
using Vint = std::vector<int>;
using Vlli = std::vector<lli>;
using Wint = std::vector<Vint>;
using Wlli = std::vector<Vlli>;
using Vbool = std::vector<bool>;
using pii = std::pair<int, int>;
using pll = std::pair<lli, lli>;

constexpr int MOD = 1e9 + 7;
constexpr int INFi = 2e9 + 1;
constexpr lli INFl = (lli)(9e18) + 1;
const vector<pii> DXDY = {std::make_pair(1, 0), std::make_pair(-1, 0), std::make_pair(0, 1), std::make_pair(0, -1)};
constexpr char BR = '\n';

#define FOR(i, a, b) for(int (i) = (a); (i) < (b); (i)++)
#define FOReq(i, a, b) for(int (i) = (a); (i) <= (b); (i)++)
#define rFOR(i, a, b) for(int (i) = (b); (i) >= (a); i--)
#define FORstep(i, a, b, step) for(int (i) = (a); i < (b); i += (step))
#define REP(i, n) FOR(i, 0, n)
#define rREP(i, n) rFOR(i, 0, (n-1))
#define vREP(ele, vec) for(auto &(ele) : (vec))
#define vREPcopy(ele, vec) for(auto (ele) : (vec))
#define SORT(A) std::sort((A).begin(), (A).end())
// 座標圧縮 (for vector) : ソートしてから使うのが一般的 ; SORT(A) => COORDINATE_COMPRESSION(A)
#define COORDINATE_COMPRESSION(A) (A).erase(unique((A).begin(),(A).end()),(A).end())



template <class T> inline int argmin(std::vector<T> vec){return min_element(vec.begin(), vec.end()) - vec.begin();}
template <class T> inline int argmax(std::vector<T> vec){return max_element(vec.begin(), vec.end()) - vec.begin();}
template <class T> inline void chmax(T &a, T b){a = max(a, b);}
template <class T> inline void chmin(T &a, T b){a = min(a, b);}
inline int toInt(string &s){int res = 0; for(char a : s) res = 10 * res + (a - '0'); return res;}
inline int toInt(const string s){int res = 0; for(char a : s) res = 10 * res + (a - '0'); return res;}
inline long long int toLong(string &s){lli res = 0; for(char a : s) res = 10 * res + (a - '0'); return res;}
inline long long int toLong(const string s){lli res = 0; for(char a : s) res = 10 * res + (a - '0'); return res;}
template <class T> inline std::string toString(T n){
  if(n == 0) return "0";
  std::string res = "";
  if(n < 0){n = -n;while(n != 0){res += (char)(n % 10 + '0'); n /= 10;}
  std::reverse(res.begin(), res.end()); return '-' + res;}
  while(n != 0){res += (char)(n % 10 + '0'); n /= 10;} std::reverse(res.begin(), res.end()); return res;
}

// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


class Solver{
  using LINE = std::vector<bool>;
  using MAP  = std::vector<LINE>;
  const int H, W;
  MAP Data;
public:
  Solver(int h, int w): H(h), W(w){
    Data.resize(H, LINE(W));
  }
  ~Solver(void){};
  void getIn(void){
    std::string s;
    REP(i, H){
      cin >> s;
      REP(j, W) Data[i][j] = (s[j] == '.');
    }
  }
  inline bool isIn(int x, int y){
    return 0 <= x and x < H and 0 <= y and y < W;
  }
  int shortest(void){
    MAP DT = Data;
    using Position = std::pair<int, int>;
    using PosAndCost = std::pair<Position, int>;
    std::queue<PosAndCost> bfs;
    bfs.push(make_pair(make_pair(0, 0), 1));
    DT[0][0] = false;
    while(not bfs.empty()){
      const PosAndCost u = bfs.front(); bfs.pop();
      const int x = u.first.first,
                y = u.first.second,
             cost = u.second;
      vREP(ele, DXDY){
        const int next_x = x + ele.first, next_y = y + ele.second;
        if(isIn(next_x, next_y) and DT[next_x][next_y]){
          if(next_x == H-1 and next_y == W-1) return cost + 1;
          bfs.push(make_pair(make_pair(next_x, next_y), cost + 1));
          DT[next_x][next_y] = false;
        }
      }
    }
    return -1;
  }
  int solve(void){
    int count_white = 0;
    REP(i, H) REP(j, W) if(Data[i][j]) count_white++;
    int k = shortest();
    return (k != -1) ? count_white - k : -1;
  }
};

int main(void){
  int h, w; cin >> h >> w;
  Solver A(h, w); A.getIn();
  cout << A.solve() << BR;
  return 0;
}

Measured memory_bytes: 256