#include <bits/stdc++.h>

using namespace std;

#define INF 1001000100010001000
#define MOD 1000000007
#define EPS 1e-10
#define int long long
#define rep(i, N) for (int i = 0; i < N; i++)
#define Rep(i, N) for (int i = 1; i < N; i++)
#define For(i, a, b) for (int i = (a); i < (b); i++)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define i_i pair<int, int>
#define vi vector<int>
#define vvi vector<vi >
#define vb vector<bool>
#define vvb vector<vb >
#define vp vector< i_i >
#define all(a) (a).begin(), (a).end()
#define Int(x) int x; cin >> x;
#define int2(x, y) Int(x); Int(y);
#define int3(x, y, z) Int(x); int2(y, z);
#define fir first
#define sec second
#define ffir first.first
#define fsec first.second
#define sfir second.first
#define ssec second.second
#define Decimal fixed << setprecision(10)

int dxy[5] = {0, 1, 0, -1, 0};
// BIT DiscreteFourierTransform FFT avl cmd cusum dijkstra dinic geo2 gin graph kruskal lca lcm matrix ncm next_combination segtree st tmp topcoder uf vi 

using Weight = int;
using Flow = int;
struct Edge {
    int s, d; Weight w; Flow c;
    Edge() {};
    Edge(int s, int d, Weight w = 1) : s(s), d(d), w(w), c(w) {};
};
bool operator<(const Edge &e1, const Edge &e2) { return e1.w < e2.w; }
bool operator>(const Edge &e1, const Edge &e2) { return e2 < e1; }
inline ostream &operator<<(ostream &os, const Edge &e) { return (os << '(' << e.s << ", " << e.d << ", " << e.w << ')'); }

using Edges = vector<Edge>;
using Graph = vector<Edges>;
using Array = vector<Weight>;
using Matrix = vector<Array>;

void addArc(Graph &g, int s, int d, Weight w = 1) {
    g[s].emplace_back(s, d, w);
}
void addEdge(Graph &g, int a, int b, Weight w = 1) {
    addArc(g, a, b, w);
    addArc(g, b, a, w);
}

//単一始点最短経路(負閉路なし)
//Dijkstra O((|E|+|V|)log|V|)
//dist: 始点から各頂点までの最短距離
//戻り値: 最短経路木の親頂点(根は-1)
vector<int> dijkstra(const Graph &g, int s, Array &dist) {
    int n = g.size();
    assert(s < n);
    enum { WHITE, GRAY, BLACK };
    vector<int> color(n, WHITE); color[s] = GRAY;
    vector<int> prev(n, -1);
    dist.assign(n, INF); dist[s] = 0;
    using State = tuple<Weight, int, int>; //始点からの最短距離 子 親
    priority_queue<State, vector<State>, greater<State>> pq; pq.emplace(0, s, -1);
    while (pq.size()) {
        Weight d; int v, u; tie(d, v, u) = pq.top(); pq.pop();
        if (dist[v] < d)continue;
        color[v] = BLACK; prev[v] = u;
        for (auto &e : g[v]) {
            if (color[e.d] == BLACK)continue;
            if (dist[e.d] > dist[v] + e.w) {
                dist[e.d] = dist[v] + e.w;
                pq.emplace(dist[e.d], e.d, v);
                color[e.d] = GRAY;
            }
        }
    }
    return prev;
}

signed main()
{
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    int2(h, w);
    vector<string> table(h);
    rep(i, h) cin >> table[i];

    int score = 0;
    rep(i, h) rep(j, w) if (table[i][j] == '.') score++;

    Graph g(h * w);
    rep(i, h) rep(j, w) {
        rep(k, 4) {
            int nx = i + dxy[k], ny = j + dxy[k+1];
            if (0 <= nx && nx < h && 0 <= ny && ny < w && 
                    table[nx][ny] == '.') {
                addArc(g, i * w + j, nx * w + ny);
            }
        }
    }
    vi yui(0);
    dijkstra(g, 0, yui);
    if (yui[h*w-1] == INF) cout << -1 << endl;
    else cout << score - yui[h*w-1] - 1 << endl;

    return 0;
}





Measured memory_bytes: 768