#include "bits/stdc++.h"
#define Rep(i,n) for(int i=0;i<(int)(n);i++)
#define For(i,n1,n2) for(int i=(int)(n1);i<(int)(n2);i++)
#define REP(i,n) for(ll i=0;i<(ll)(n);i++)
#define RREP(i,n) for(ll i=((ll)(n)-1);i>=0;i--)
#define FOR(i,n1,n2) for(ll i=(ll)(n1);i<(ll)(n2);i++)
#define RFOR(i,n1,n2) for(ll i=((ll)(n1)-1);i>=(ll)(n2);i--)
#define all(a)  (a).begin(),(a).end()
#define IOS std::cin.tie(0),std::ios::sync_with_stdio(false)

namespace idaten {

	using namespace std;
	using ll = int_fast64_t;
	using ull = uint_fast64_t;
	using P = std::pair<int64_t, int64_t>;
	template<typename T1, typename T2> inline bool chmin(T1& a, T2 b) { if (a > b) { a = b; return 1; }return 0; }
	template<typename T1, typename T2> inline bool chmax(T1& a, T2 b) { if (a < b) { a = b; return 1; }return 0; }
	template<class Type>struct is_vector : std::false_type {};
	template<class ValueType, class Alloc>struct is_vector<std::vector<ValueType, Alloc>> : std::true_type {};
	template <typename T> inline std::ostream& operator << (std::ostream& out, const std::vector<T>& v) {
		if (v.empty())return out;
		constexpr bool is_vector_v = is_vector<T>::value;
		if (is_vector_v)for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? "\n" : "");
		else for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? " " : "");
		return out;
	}
	inline void put() {}
	template<class T> inline void put(const T& first) { std::cout << first << "\n"; }
	template<class T, class... N> inline void put(const T& first, const N& ... rest) { std::cout << first << " "; put(rest...); }
	inline void putn() {}
	template<class T, class... N> inline void putn(const T& first, const N& ... rest) { std::cout << first << "\n"; putn(rest...); }

	template<typename T>
	class Grid {
	private:
		int dy[8] = { 1,-1,0,0,1,1,-1,-1 };
		int dx[8] = { 0,0,1,-1,1,-1,1,-1 };
	public:
		vector<vector<T>> g;
		int h;
		int w;
		Grid(int h, int w):h(h),w(w) {
			init(h, w);
		}
		void init(int h, int w) {
			g.resize(h);
			for (int i = 0; i < h; ++i) {
				g[i].resize(w);
			}
		}
		void input() {
			for (int i = 0; i < h; ++i) {
				for (int j = 0; j < w; ++j) {
					cin >> g[i][j];
				}
			}
		}
		bool incl(int y, int x) {
			return 0 <= y && y < h && 0 <= x && x < w;
		}
		int to_num(int y, int x) {
			return y * w + x;
		}
		pair<int, int> to_cor(int num) {
			return pair<int, int>(num / w, num % w);
		}
		vector<vector<int>> to_graph(T disable, int arround=4) {
			vector<vector<int>> path(h * w);
			for (int i = 0; i < h; i++) {
				for (int j = 0; j < w; j++) {
					if (g[i][j] != disable) {
						for (int k = 0; k < arround; k++) {
							int ny = i + dy[k];
							int nx = j + dx[k];
							if (incl(ny, nx) && g[ny][nx]!= disable) {
								int now = to_num(i, j);
								int next = to_num(ny, nx);
								path[now].push_back(next);
							}
						}
					}
				}
			}
			return path;
		}
	};

	void solve() {
		IOS;
		int h, w;
		cin >> h >> w;
		Grid<char> g(h, w);
		g.input();
		auto path = g.to_graph('#');
		queue<int> q;
		vector<int> d(h * w, -1);
		if (g.g[0][0] == '.') {
			q.push(0);
			d[0] = 0;
		}
		while (!q.empty()) {
			int p = q.front();
			q.pop();
			REP(i, path[p].size()) {
				int t = path[p][i];
				if (d[t] < 0) {
					d[t] = d[p] + 1;
					q.push(t);
				}
			}
		}
		int cnt = 0;
		REP(i, h) {
			REP(j, w) {
				if (g.g[i][j] == '#') {
					cnt++;
				}
			}
		}
		if (d[h * w - 1] < 0) {
			put(-1);
		} else {
			put(h * w - 1 - cnt - d[h * w - 1]);
		}
	}
} // namespace idaten

int main() {
	idaten::solve();
	return 0;
}


Measured memory_bytes: 384