#include <bits/stdc++.h>
#include <boost/multiprecision/cpp_int.hpp>
using namespace std;

//#define int long long
using bll = boost::multiprecision::cpp_int;
using ll = long long;
//constexpr int INF = 1e9;//INT_MAX=(1<<31)-1=2147483647
constexpr ll INF = (ll)1e18;//(1LL<<63)-1=9223372036854775807
constexpr ll MOD = (ll)1e9 + 7;
constexpr double EPS = 1e-9;
constexpr int dx[4]={1,0,-1,0};
constexpr int dy[4]={0,1,0,-1};
#ifdef LOCAL_ENV
	#define debug(var) std::cout<<#var" = "<<var<<std::endl
#else
	#define debug(var)
#endif
#define p(var) std::cout<<var<<std::endl
#define PI (acos(-1))
#define rep(i, n)   for(ll i=0, i##_length=(n); i< i##_length; ++i)
#define repeq(i, n) for(ll i=1, i##_length=(n); i<=i##_length; ++i)
#define all(v) (v).begin(), (v).end()
#define uniq(v) (v).erase(unique((v).begin(), (v).end()), (v).end());
template<typename T> inline void pv(vector<T> v) { for(ll i=0, N=v.size()-1; i<=N; i++) if(i!=N) cout << v[i] << ' '; else cout << v[i] << endl; }
template<typename T> inline T power(T x, T n){ return n ? power(x*x%MOD,n/2)*(n%2?x:1)%MOD : 1; }
template<typename T> inline T gcd(T a, T b) { return b ? gcd(b,a%b) : a; }
template<typename T> inline T lcm(T a, T b) { return a / gcd(a,  b) * b; }
template<typename T1, typename T2>inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template<typename T1, typename T2>inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }
template<typename T1, typename T2> ostream& operator<<(ostream& s, const pair<T1, T2>& p) {return s << "(" << p.first << ", " << p.second << ")";}
template<typename T> ostream& operator<<(ostream& s, const vector<T>& v) {
	for (int i = 0, len = v.size(); i < len; ++i){
		s << v[i]; if (i < len - 1) s << "\t";
	}
	return s;
}
template<typename T> ostream& operator<<(ostream& s, const vector< vector<T> >& vv) {
	for (int i = 0, len = vv.size(); i < len; ++i){
		s << vv[i] << endl;
	}
	return s;
}
template<typename T1, typename T2> ostream& operator<<(ostream& s, const map<T1, T2>& m) {
	s << "{" << endl;
	for (typeof(m.begin()) itr = m.begin(); itr != m.end(); ++itr){
		s << "\t" << (*itr).first << " : " << (*itr).second << endl;
	}
	s << "}" << endl;
	return s;
}

/*-----8<-----8<-----*/

queue<pair<int,int>> que;
vector<string> s;
vector<vector<ll>> len; 
int H,W;

int bfs(){
	while (!que.empty()) {
		auto v = que.front(); // キューから先頭頂点を取り出す
		que.pop();

        rep(i,4){
            int nx=v.first+dx[i];
            int ny=v.second+dy[i];
            if(nx==H-1 && ny==W-1){
                return len[v.first][v.second]+1;
            }
            if(nx==-1 || ny==-1 || nx==H || ny==W || s[nx][ny]=='#')continue;
            if(!len[nx][ny]){
                len[nx][ny]=len[v.first][v.second]+1;
                que.push(make_pair(nx,ny));
            }
        }
	}
    return -1;
}


signed main() {

    cin >> H >> W;
    s.assign(H,"");
    rep(i,H)cin>>s[i];

    int kuro=0,shiro=0;
    rep(i,H)rep(j,W){
        if(s[i][j]=='.')shiro++;
        else kuro++;
    }

    len = vector<vector<ll>>(H, vector<ll>(W, 0));
    len[0][0]=1;
    que.push(make_pair(0,0));
    int minlen=bfs();
    if(minlen>0) p(shiro-minlen);
    else p(-1);

    return 0;
}


Measured memory_bytes: 256