#include <bits/stdc++.h>
#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define INF 999999999
#define M_PI 3.14159265358979323846
#define ALL(X) (X).begin(),(X).end()

#ifdef __LOCAL
    #define DBG(X) cout << #X << " = " << (X) << endl;
    #define SAY(X) cout << (X) << endl;
#else
    #define DBG(X)
    #define SAY(X)
#endif

#ifdef __LOCAL
    #include <filesystem>
    namespace fs = std::filesystem;
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[]={1, 0, -1, 0};
int dy[]={0, 1, 0, -1};
const int INT_INF = (int)(2e9);
const ll  LL_INF = (ll)(2e18);
const int NIL = -1;
static mt19937 _g(time(nullptr));
 
std::string pad(int num){ char buffer[4]; std::snprintf(buffer, sizeof(buffer), "%03d", num); return buffer;}
inline ll randint(ll a, ll b) { ll w = (_g() << 31LL) ^ _g(); return a + w % (b - a + 1); }
inline void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); };
template<typename T> inline T sign(T x) { return T(x > 0) - T(x < 0); }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const pair<T, S> p) { cout << "[" << p.first << ";" << p.second << "]"; return os; }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const map<T, S> p) { for (auto el : p) cout << "[" << el.first << "," << el.second << "] "; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const vector<T>& v) { for (auto el : v) cout << el << " "; return os; }
template<typename T> inline T fetch() { T ret; cin >> ret; return ret; }
template<typename T> inline vector<T> fetch_vec(int sz) { vector<T> ret(sz); for (auto& elem : ret) cin >> elem; return ret; }

int H,W;
vector<string> S;

void input(){
    #ifdef __LOCAL
        fs::path path_to_file = __FILE__;
        fs::path input,output;
        input = output = path_to_file.parent_path();
        input += string("/input/") + string(path_to_file.stem()) + string(".txt");
        output += string("/output/") + string(path_to_file.stem()) + string(".txt");
        freopen(input.c_str(), "r", stdin);
        freopen(output.c_str(), "w", stdout);
    #endif
    cin >> H >> W;
    REP(i,H){
        string s;
        cin >> s;
        S.push_back(s);
    }
}

bool isOut(pii x){
    return (x.first<0||x.second<0||x.first>=H||x.second>=W);
}

bool isWall(pii x){
    return (S[x.first][x.second]=='#');
}

bool arrival=false;
int bfs(pii s){
    map<pii,int> step;
    map<pii,bool> visited;
    queue<pii> q;
    q.push(s);
    step[s]=0;
    while(!q.empty()){
        pii now=q.front();
        q.pop();
        visited[now]=true;
        if(visited[{H-1,W-1}]) {arrival=true; break;}
        REP(k,4){
            pii next = {now.first+dx[k], now.second+dy[k]};
            if(visited[next]) continue;
            if(isOut(next)) continue;
            if(isWall(next)) continue;
            step[next]=step[now]+1;
            q.push(next);
            visited[next]=true;
        }
    }
    return step[{H-1,W-1}]+1;
}

int num_wall(){
    int ret=0;
    REP(i,H) REP(j,W) ret+=(S[i][j]=='#');
    return ret;
}

int solve(){
    input();
    int numW = num_wall();
    int step = bfs({0,0});
    int ans = arrival?(H*W-step-numW):-1;
    cout << ans << endl;
    return 0;
}

int maketestcase(){
    #ifdef __LOCAL
        fs::path path_to_file = __FILE__;
        fs::path input,output;
        input = output = path_to_file.parent_path();
        input += string("/input/") + string(path_to_file.stem()) + string(".txt");
        freopen(input.c_str(), "w", stdout);
    #endif
    int h,w;
    h=50,w=50;
    vector<string> s(h);
    REP(i,h) REP(_,w) s[i]+= ".";
    cout << h << " " << w << endl;
    for(auto x:s) cout << x << endl;
    return 0;
}

int main(){
    solve();
    // maketestcase();
    return 0;
}


Measured memory_bytes: 640