// だーれだ？
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//  . TMHHbZl=1.   _~::::::(<::<:<___-___:<<:::::jX3=. ` ` `,MMHM@@@@Mg@@@@@@@@@H@
//
#include <bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<(b);++i)
#define erep(i,a,b) for(int i=a;i<=(b);++i)
#define per(i,a,b) for(int i=(a);i>(b);--i)
#define eper(i,a,b) for(int i=(a);i>=b;--i)
#define fore(i, x, a) for(auto &&x:a) 
#define ITR(i,b,e) for(auto i=(b);i!=(e);++i)
#define IN(i,a,b) (a)<=(i) && (i)<(b)
#define debug(x)  cout << #x << " = " << (x) << endl;
#define pb push_back
#define mp make_pair
#define MOD 1000000007
#define ALL(x) begin(x),end(x)
#define F first
#define S second
#define debug(x)  cout << #x << " = " << (x) << endl;
const int inf=1001001001; const long long INF=1001001001001001001;
using namespace std;
using ll = long long;
using pii = pair<int,int>;
using vii = vector<int>;
using vll = vector<ll>;
template<class T>using  PS_queue = priority_queue<T, vector<T>, greater<T> >;
template<class T>using vv = vector<T>;
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 (b<a) { a = b; return 1; } return 0; }
template<typename A, size_t N, typename T> void Fill(A (&array)[N], const T &val){fill( (T*)array, (T*)(array+N), val );}
template<class T> ostream& operator<<(ostream &os,const vector<T> &v) {
    ITR(i,begin(v),end(v))os<<*i<<(i==end(v)-1?"":" ");return os;}
template<class T> istream& operator>>(istream &is,vector<T> &v) {
    ITR(i,begin(v),end(v)) is>>*i;return is;}
template<class T,class U> istream& operator>>(istream &is, pair<T,U> &p) {
    is>>p.first>>p.second;return is;}
template<class T>T gcd(T a, T b){ return b ? gcd(b, a % b) : a; }
template<class T>T lcm(T a, T b){ return a / gcd(a, b) * b; }
struct edge { int to, from, cost; };
int dy[]={0, 1, -1, 0}; int dx[]={1, 0, 0, -1};

int H, W, d[51][51];
string s[51];
int main() {
 cin.tie(0);
 ios::sync_with_stdio(false);
  cin >> H >> W;
  int black = 0;
  rep(i, 0, H) {
    cin >> s[i];
    rep(j, 0, W) if (s[i][j] == '#') black++;
  }
  rep(i, 0, H) fill(d[i], d[i] + W, inf);
  queue<pii> que;
  que.push(mp(0, 0));
  d[0][0] = 0;
  while (!que.empty()) {
    pii p = que.front(); que.pop();
    int y = p.F, x = p.S;
    if (y == H-1 && x == W-1) break;
    rep(i, 0, 4) {
      int nx = x + dx[i], ny = y + dy[i];
      if (IN(ny, 0, H) && IN(nx, 0, W) && d[ny][nx] == inf && s[ny][nx] != '#') {
        que.push(mp(ny, nx));
        d[ny][nx] = d[y][x] + 1;
      }
    }
  }
  if (d[H-1][W-1] == inf) cout << -1 << endl;
  else cout << H * W - black - d[H-1][W-1] - 1 << endl; 
  return 0;
}



Measured memory_bytes: 256