/*
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*/
#include "bits/stdc++.h"
using namespace std;
#define ok1 printf("ok1\n");
#define ok2 printf("ok2\n");
#define M 1000000000000000000LL
#define rep(i,n) for(int i=0;i<n;++i)
#define REP(i,s,n) for(int i=(s);i<(n);++i)
#define repr(i,n) for(int i=n-1;i>=0;--i)
#define REPR(i,s,n) for(int i=(s);i>=(n);--(i))
#define all(a) (a).begin(),(a).end()
#define reall(a) (a).rbegin(),(a).rend()
#define pb push_back
#define pf push_front
#define MIN(a,b) a=min((a),(b))
#define MAX(a,b) a=max((a),(b))
#define SIZE(v) (int)v.size()
#define DOUBLE fixed << setprecision(15)
#define fi first
#define se second
const double pi = acos(-1.0);
typedef vector<int> vi;
typedef vector<string> vs;
typedef long long ll;
typedef vector<ll> vll;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef vector<char> vc;
typedef vector<double> vd;
typedef vector<bool> vb;
typedef deque<ll> dll;
typedef pair<ll, ll> P;
typedef vector<P> vP;
const ll mod = 1e9 + 7;
//const ll mod = 998244353;
ll dy[4] = { 1,0,-1,0 };
ll dx[4] = { 0,1,0,-1 };
struct edge {
	int to;
	int cost;
};
bool out_check(ll a, ll b) {
	if (0 <= a && a < b) return true;
	else return false;
}
void Pvll(vll v) {
	cout << "------------------------------------------------\n";
	rep(i, v.size()) cout << v[i] << " ";
	cout << endl;
	cout << "------------------------------------------------\n";
}
void Pvvll(vvll v) {
	cout << "------------------------------------------------\n";
	rep(i, v.size()) {
		rep(j, v[i].size()) {
			cout << v[i][j] << " ";
		}
		cout << endl;
	}
	cout << "------------------------------------------------\n";
}

void Ps(string s) {
	cout << "------------------------------------------------\n";
	rep(i, s.size()) cout << s[i] << " ";
	cout << endl;
	cout << "------------------------------------------------\n";
}

void Pvs(vs s) {
	cout << "------------------------------------------------\n";
	rep(i, s.size()) {
		rep(j, s[i].size()) {
			cout << s[i][j] << " ";
		}
		cout << endl;
	}
	cout << "------------------------------------------------\n";
}

void Yes(bool x) {
	if (x) cout << "Yes\n";
	else cout << "No\n";
}

void YES(bool x) {
	if (x) cout << "YES\n";
	else cout << "NO\n";
}

void yes(bool x) {
	if (x) cout << "yes\n";
	else cout << "no\n";
}

void Yay(bool x) {
	if (x) cout << "Yay!\n";
	else cout << ":(\n";
}

ll  n, d, r, l, k, h, ans = 0, ret = M;
bool flag = false, flag2 = false, flag3 = false;
//string s, t, u;

void INIT() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	cout << DOUBLE;
}

int main() {
	INIT();
	ll w;
	cin >> h >> w;
	vs s(h);
	rep(i, h) cin >> s[i];
	rep(i, h) rep(j, w) ans += (bool)(s[i][j] == '.');
	queue<pair<ll,P>> qu;
	qu.push(make_pair(1,make_pair(0, 0)));
	vvll cost(h, vll(w,0));
	while (!qu.empty()) {
		ll y = qu.front().second.first, x = qu.front().second.second, a = qu.front().first;
		//cout << y << " " << x << " " << qu.front().first << endl;
		qu.pop();
		if (cost[y][x]) continue;
		cost[y][x] = a;
		rep(i, 4) {
			ll X = x + dx[i], Y = y + dy[i];
			if (out_check(X, w) && out_check(Y, h) && s[Y][X] == '.') {
				//cout << Y << " " << X << endl;
				qu.push(make_pair((a + 1), make_pair(Y, X)));
			}
		}
	}
	//Pvvll(cost);
	if (cost[h - 1][w - 1]) cout << ans - cost[h - 1][w - 1] << endl;
	else cout << -1 << endl;
	return 0;
}

Measured memory_bytes: 256