import std.stdio, std.conv, std.string;
import std.algorithm, std.array, std.container, std.typecons;
import std.numeric, std.math;
import core.bitop;

T RD(T = string)() { static string[] ss; while(!ss.length) ss = readln.chomp.split; string res = ss[0]; ss.popFront; return res.to!T; }
string RDR()() { return readln.chomp; }
T[] ARR(T)(in string str) { return str.split.to!(T[]); }
size_t[] MAKE_IDX(alias less = "a < b", Range)(Range range) { auto idx = new size_t[](range.length); makeIndex!(less)(range, idx); return idx;}
size_t MIN_POS(alias less = "a < b", Range)(Range range) { auto r = minPos!(less)(range); return range.length - r.length; }

bool INSIDE(T)(T x, T b, T e) { return x >= b && x < e; }

long mod = pow(10, 9) + 7;
void moda(ref long x, long y) { x = (x + y) % mod; }
void mods(ref long x, long y) { x = ((x + mod) - (y % mod)) % mod; }
void modm(ref long x, long y) { x = (x * y) % mod; }

struct UnionFind
{
	void init(long n) { par = new long[](n); foreach (i; 0..n) par[i] = i; }
	long root(long i) { return par[i] == i ? i : (par[i] = root(par[i])); }
	bool same(long i, long j) { return root(i) == root(j); }
	void unite(long i, long j) { i = root(i); j = root(j); if (i == j) return; par[i] = j; }
	long[] par;
}

void main()
{
	auto H = RD!long;
	auto W = RD!long;
	string[] s;
	foreach (i; 0..H)
	{
		s ~= RD!string;
	}

	long[3][] open;
	open ~= [0, 0, 1];
	auto close = new long[][](H, W);
	long[2][4] dir = [[-1, 0], [1, 0], [0, -1], [0, 1]];
	long cost = -1;
	while (!open.empty)
	{
		auto node = open.front;
		open.popFront;
		if (node[0] == H - 1 && node[1] == W - 1)
		{
			cost = node[2];
			break;
		}
		foreach (d; dir)
		{
			auto y = node[0] + d[0];
			auto x = node[1] + d[1];
			if (!INSIDE(y, 0, H) || !INSIDE(x, 0, W)) continue;
			if (close[y][x] == 1 || s[y][x] == '#') continue;
			open ~= [y, x, node[2] + 1];
			close[y][x] = 1;
		}
	}
	if (cost == -1)
	{
		writeln("-1");
	}
	else
	{
		long ans;
		foreach (e; s)
		{
			foreach (ee; e)
			{
				if (ee == '.') ++ans;
			}
		}
		ans -= cost;
		writeln(ans);
	}

	stdout.flush();
}