#include <bits/stdc++.h>
using namespace std;
 
using ll = long long;
using ld = long double;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
#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 REP(i, n) FOR(i, 0, (n))
#define REPR(i, n) FORR(i, (n) - 1, 0)
#define REP1(i, n) FOR(i, 1, (n) + 1)
#define REPS(c, s) for (char c : s)
#define ALL(c) (c).begin(), (c).end()
#define SORT(c) sort(ALL(c))
#define REV(c) reverse(ALL(c))
#define sz(v) (int)v.size()
#define endl '\n'
template<class T> inline bool chmin(T& a, T b) {if (a > b) {a = b; return true;} return false;}
template<class T> inline bool chmax(T& a, T b) {if (a < b) {a = b; return true;} return false;}
template<class T> inline void printv(vector<T>& v) {int n = sz(v); REP(i, n) cout << v[i] << (i == n - 1 ? endl : ' ');}
const int MOD = 1000000007;
const int INF = 1000000001;
const ll LINF = 1000000001000000001LL;
 
void solve();
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(numeric_limits<double>::max_digits10);
    solve();
    return 0;
}

class UnionFind {
    vector<int> parent;

    public:
        UnionFind(int size) {
            parent = vector<int>(size, -1);
        }

        int find(int x) {
            if (parent[x] < 0) {
                // parent itself
                return x;
            } else {
                return parent[x] = find(parent[x]);
            }
        }

        bool unite(int x, int y) {
            int rX, rY;
            if ((rX = find(x)) == (rY = find(y))) {
                // already united
                return false;
            }
            if (size(rX) < size(rY)) {
                int tmp = rX;
                rX = rY;
                rY = tmp;
            }
            parent[rX] += parent[rY];
            parent[rY] = rX;
            return true;
        }

        int size(int x) {
            return -parent[find(x)];
        }

        bool is_same(int x, int y) {
            return find(x) == find(y);
        }

        // CAUTION!! : This method is heavy due to scanning linearly.
        int component_count() {
            int c = 0;
            for (const int x : parent) {
                if (x < 0) {
                    c++;
                }
            }
            return c;
        }
};

void solve() {
    int h, w;
    cin >> h >> w;
    vector<string> m(h + 2);
    m[0] = string('#', w + 2);
    m[h + 1] = string('#', w + 2);
    int white = 0;
    string s;
    REP1(i, h) {
        cin >> s;
        m[i] = '#' + s + '#';
        REPS(c, s) if (c == '.') white++;
    }

    deque<tuple<int, int, int>> q;
    q.emplace_back(1, 1, 1);
    m[1][1] = '#';

    vi x{1, 0, -1, 0};
    vi y{0, -1, 0, 1};

    int r, c, d;
    while (!q.empty()) {
        tie(r, c, d) = q.front(); q.pop_front();
        if (r == h && c == w) {
            cout << white - d << endl;
            return;
        }

        REP(i, 4) {
            if (m[r + y[i]][c + x[i]] == '.') {
                q.emplace_back(r + y[i], c + x[i], d + 1);
                m[r + y[i]][c + x[i]] = '#';
            }
        }
    }

    cout << -1 << endl;

}


Measured memory_bytes: 256