/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author champon
 */

#include <iostream>
#include <fstream>
#include<bits/stdc++.h>
#define se cout << "test ok" << endl;
#define sp << " " <<
#define enl "\n"
using namespace std;
using ll = long long;
using ld = long double;
using vi = vector<int>;
using vii = vector<vector<int>>;
using vl = vector<ll>;
using vll = vector<vector<ll>>;
using vc = vector<char>;
using vcc = vector<vector<char>>;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
ll mod = ll(1e9)+7;
ll inf = ll(1e18);
void bl(bool b, ostream& out=cout){ out << (b ? "Yes" : "No") << endl; }
void bl2(bool b, ostream& out=cout){ out << (b ? "YES" : "NO") << endl; }
template<typename T> inline bool chmax(T &a, T b){ if(a<b){a=b; return true;} return false; }
template<typename T> inline bool chmin(T &a, T b){ if(a>b){a=b; return true;} return false; }
int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
int dy[] = {0, 1, 0, -1, 1, -1, -1, 1};

#ifndef INCLUDE_DEBUG_HPP
#define INCLUDE_DEBUG_HPP

#include <iostream>
#include <vector>
#include <map>
using namespace std;

namespace dbg {
    using ll = long long;

    class Debug {
    public:
        Debug(){}
        template<typename T>
        void vd(vector<T> vec);
        template<typename T>
        void vd2(vector<vector<T>> vec);
        template<typename T>
        void ad(T *arr, ll n);
        template<typename T, size_t N>
        void ad2(T (&arr)[N], ll n);
        template<typename T>
        void md(T mp);
    };

    template<typename T>
    void Debug::vd(vector<T> vec) {
        for (auto vv : vec) cout << vv << " ";
        cout << endl;
    }

    template<typename T>
    void Debug::vd2(vector<vector<T>> vec) {
        for (auto vv : vec) {
            for (auto vvv : vv) cout << vvv << " ";
            cout << endl;
        }
    }

    template<typename T>
    void Debug::ad(T *arr, ll n) {
        for (int i = 0; i <= n; i++) cout << arr[i] << " ";
        cout << endl;
    }

    template<typename T, size_t N>
    void Debug::ad2(T (&arr)[N], ll n) {
        for (int i = 0; i <= N; i++) for (int j = 0; j <= n; j++) cout << arr[i][j] << " ";
        cout << endl;
    }

    template<typename T>
    void Debug::md(T mp) {
        cout << "key : value" << endl;
        for (auto const &m : mp) cout << m.first << " : " << m.second << endl;
        cout << endl;
    }

}

#endif //INCLUDE_DEBUG_HPP

using dbg::Debug;
Debug debug;

class DGridRepainting {
public:
	void solve(std::istream& in, std::ostream& out) {
	    int h, w;
	    in >> h >> w;

	    vcc g(h, vc(w));
        string s;
        ll res = h*w;
	    for(int i=0; i<h; i++){
	        in >> s;
	        for(int j=0; j<w; j++){
                g[i][j] = s[j];
                if(s[j] == '#') res--;
	        }
	    }

        queue<pi> q;
	    q.push(make_pair(0 , 0));
	    vll dist(h, vl(w, inf));
	    dist[0][0] = 1;
	    while(!q.empty()){
            pi u = q.front();
            q.pop();
            for(int i=0; i<4; i++){
                int ny = u.first + dy[i];
                int nx = u.second + dx[i];
                if(ny < 0 || nx < 0 || nx >= w || ny >= h) continue;
                if(g[ny][nx] == '#') continue;
                if(dist[ny][nx] > dist[u.first][u.second] + 1){
                    dist[ny][nx] = dist[u.first][u.second] + 1;
                    q.push(make_pair(ny, nx));
                }
            }
	    }

        if(dist[h-1][w-1] == inf) out << -1 << enl;
        else out << res-dist[h-1][w-1] << enl;
	}
};


int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
	DGridRepainting solver;
	std::istream& in(std::cin);
	std::ostream& out(std::cout);
	solver.solve(in, out);
	return 0;
}


Measured memory_bytes: 256