#include <bits/stdc++.h>
using namespace std;

/***** type *****/
using ll = long long;
using ld = long double;
template <class T> using vt = vector<T>;
template <class T> using vvt = vector<vector<T>>;
template <class T> using vvvt = vector<vector<vector<T>>>;
template <class T> using uset = unordered_set<T>;
template <class T1, class T2> using umap = unordered_map<T1, T2>;

/***** define *****/
#define all(c) (c).begin(), (c).end()            // begin to end
#define coutld cout << fixed << setprecision(10) // cout long double
#define rep(i, b, e) for (ll i = b; i < e; i++)  // repeat
#define repr(i, b, e) for (ll i = b; e < i; i--) // repeat reverse
#define val(itr) *(itr)                          // get value
#define pair NyaaPair                            // nyaa pair
#define first f                                  // pair::first
#define second s                                 // pair::second
/***** const value *****/
#define llong_max 9223372036854775807            // 9 * 10^18
#define ldbl_max 1.79769e+308                    // 1.7 * 10^308
#define pi 3.1415926535897932                    // 3.14 ...
#define loop_end 9223372036854775806             // LLONG_MAX-1
/***** for each macro *****/
#define fori(i, ...) if(ll i = -1) for(__VA_ARGS__) if(i++, true)
#define each(i, e, c) fori(i, auto e = c.begin(); e != c.end(); ++e)
#define forir(i, v, ...) if(ll i=(ll)v.size())for(__VA_ARGS__)if(i--,true)
#define eachr(i, e, c) forir(i, auto e = c.rbegin(); e != c.rend(); ++e)

/***** lambda *****/
auto Count = [] // long long count value
(auto b, auto e, auto x) { return (ll)count(b, e, x); };
auto CtoN = [] // char to number
(auto c) { return (ll)(c - '0'); };
auto CeilD = [] // long double ceiling div
(auto a, auto b) { return ceil((ld)a / (ld)b); };
auto Fix = [] // fix value
(auto b, auto e, auto fix)
{ for (auto it = b; it != e; ++it) *it += fix; };
auto NtoC = [] // number to char
(auto n) { return (char)('0' + n); };
auto Pow = [] // long long pow
(auto a, auto b) { return (ll)pow(a, b); };
auto Pow2 = [] // long long pow2
(auto n) { return (1LL << n); };
auto Pow10 = [] // long long pow10
(auto n) { return (ll)pow(10, n); };
auto Size = []  // long long collection size
(auto& c) { return (ll)(c).size(); };
auto Sum = [] // long long accumulate
(auto b, auto e) { return accumulate(b, e, 0LL); };

/***** template *****/
template <class T> void MakeVVT
(ll ys, ll xs, vvt<T>& v, T fill = T())
{	// vector<vector<T>> resize + fill
	v.resize(ys); rep(y, 0, ys) v[y].resize(xs, fill);
}
template <class T> void MakeVVVT
(ll zs, ll ys, ll xs, vvvt<T>& v, T fill = T())
{	// vector<vector<vector<T>>> resize + fill
	v.resize(zs); rep(z, 0, zs) MakeVVT(ys, xs, v[z], fill);
}
template <class T> void InputVT
(ll xs, vt<T>& v, T fix = T())
{	// input vector<T> (T != struct) + fix
	v.resize(xs); rep(i, 0, xs) { cin >> v[i]; v[i] += fix; }
}
template <class T> void InputVVT
(ll ys, ll xs, vvt<T>& v, T fix = T())
{	// input vector<vector<T>> (T != struct) + fix
	MakeVVT(ys, xs, v, fix);
	rep(y, 0, ys) rep(x, 0, xs) { cin >> v[y][x]; v[y][x] += fix; }
}
template <class T> void InputVVVT
(ll zs, ll ys, ll xs, vvvt<T>& v, T fix = T())
{	// input vector<vector<vector<T>>> (T != struct) + fix
	v.resize(zs); rep(z, 0, zs) InputVVT(ys, xs, v[z], fix);
}
template <class T1, class T2> struct NyaaPair
{	// nyaa pair template
	T1 f; T2 s;
};
template <class T1, class T2> bool operator <
(const NyaaPair<T1, T2>& l, const NyaaPair<T1, T2>& r)
{	// nyaa pair template operator <
	return (l.f != r.f) ? l.f < r.f : l.s < r.s;
}
template <class T1, class T2> bool operator >
		(const NyaaPair<T1, T2>& l, const NyaaPair<T1, T2>& r)
{	// nyaa pair template operator >
	return (l.f != r.f) ? l.f > r.f : l.s > r.s;
}

/**************************************/
/********** BEGIN OF NYA LIB **********/
/**************************************/

namespace NyaGadget {}

namespace NyaGadget
{
	/**
	@brief グリッド上の最短経路を得る
	@param grid 二次元グリッド
	@param start 開始地点の文字
	@param wall 壁となる文字
	@return 最短経路(到達できない場合は-1)
	@note
	 予めグリッドに開始地点文字を書き込んでおく必要があることに注意。
	 単一始点最短経路を戻り値から返す。計算量 O(HW)
	**/
	vector<vector<long long>> GT_GridBFS
	(vector<vector<char>>& grid, char start, const char& wall = '#')
	{
		const long long vx[] = { 0, 1, 0, -1 }, vy[] = { 1, 0, -1, 0 };
		vector<vector<long long>> min_cost(grid.size(), vector<long long>(grid[0].size(), -1));
		queue<pair<long long, long long>> q;
		for (long long i = 0; i < (long long)grid.size(); i++)
		{
			for (long long j = 0; j < (long long)grid[i].size(); j++)
			{
				if (grid[i][j] == start)
				{
					q.push({ i, j });
					min_cost[i][j] = 0;
				}
			}
		}
		while (!q.empty())
		{
			auto p = q.front(); q.pop();
			for (long long i = 0; i < 4; i++)
			{
				long long ny = p.first + vy[i], nx = p.second + vx[i];
				if ((nx >= 0 && ny >= 0 
					&& nx < (long long)grid[0].size() && ny < (long long)grid.size()) 
					&& min_cost[ny][nx] == -1 && grid[ny][nx] != wall)
				{
					min_cost[ny][nx] = min_cost[p.first][p.second] + 1;
					q.push({ ny, nx });
				}
			}
		}
		return min_cost;
	}
}

/**************************************/
/*********** END OF NYA LIB ***********/
/**************************************/

using namespace NyaGadget;
//using mll = ModLL< 1000000007 >;

int main(void)
{
	ll H, W; cin >> H >> W;
	vvt<char> grid; InputVVT(H, W, grid);
	
	grid[0][0] = 's';
	vvt<ll> res = GT_GridBFS(grid, 's');

	ll cntw = 0;
	rep(y, 0, H) rep(x, 0, W)
	{	// 壁の数をカウント
		if (grid[y][x] == '#') cntw++;
	}

	// 開始地点も減算する必要があることに注意
	if (res[H - 1][W - 1] == -1) cout << -1;
	else cout << H * W - res[H - 1][W - 1] - cntw - 1;
	return 0;
}


Measured memory_bytes: 256