#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Edge = int;
using Graph = vector<vector<Edge>>;
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define SORT(v) sort((v).begin(), (v).end())
#define RSORT(v) sort((v).rbegin(), (v).rend())
const ll MOD = 1000000007;
const ll nmax = 8;
const ll INF = 1e9;
bool graph[nmax][nmax];
vector<vector<ll>> dist = vector<vector<ll>>(nmax, vector<ll>(nmax, INF));
struct SegmentTree
{
private:
    ll n;
    vector<ll> node;

public:
    SegmentTree(vector<ll> v)
    {
        ll sz = v.size();
        n = 1;
        while (n < sz)
        {
            n *= 2;
        }
        node.resize(2 * n - 1, INF);

        for (ll i = 0; i < sz; i++)
        {
            node[i + n - 1] = v[i];
        }

        for (ll i = n - 2; i >= 0; i--)
        {
            node[i] = min(node[2 * i + 1], node[2 * i + 2]);
        }
    }
    void update(ll x, ll val)
    {
        x += (n - 1);
        node[x] = val;
        while (x > 0)
        {
            x = (x - 1) / 2;
            node[x] = min(node[2 * x + 1], node[2 * x + 2]);
        }
    }

    // findは半開区間で考える
    ll find(ll a, ll b, ll k = 0, ll l = 0, ll r = -1)
    {
        if (r < 0)
            r = n;

        if (r <= a || b <= l)
            return INF;

        if (a <= l && r <= b)
            return node[k];

        ll vl = find(a, b, 2 * k + 1, l, (l + r) / 2);
        ll vr = find(a, b, 2 * k + 2, (l + r) / 2, r);
        return min(vl, vr);
    }
};
void warshall_floyd(ll n)
{
    for (size_t i = 0; i < n; i++)
    {
        for (size_t j = 0; j < n; j++)
        {
            for (size_t k = 0; k < n; k++)
            {
                dist[j][k] = min(dist[j][k], dist[j][i] + dist[i][k]);
            }
        }
    }
}

class UnionFind
{
public:
    vector<ll> Parent;

    UnionFind(ll N)
    {
        Parent = vector<ll>(N, -1);
    }
    ll find(ll A)
    {
        if (Parent[A] < 0)
            return A;
        return Parent[A] = find(Parent[A]);
    }

    ll size(ll A)
    {
        return -Parent[find(A)];
    }

    bool Union(ll A, ll B)
    {
        A = find(A);
        B = find(B);
        if (A == B)
        {
            return false;
        }
        if (size(A) < size(B))
            swap(A, B);

        Parent[A] += Parent[B];
        Parent[B] = A;

        return true;
    }
};

ll gcd(ll a, ll b)
{
    if (b == 0)
        return a;
    return gcd(b, a % b);
}

ll lcm(ll a, ll b)
{
    ll g = gcd(a, b);
    return a / g * b;
}

ll mulMod(ll a, ll b)
{
    return (((a % MOD) * (b % MOD)) % MOD);
}

ll powMod(ll a, ll p)
{
    if (p == 0)
    {
        return 1;
    }
    else if (p % 2 == 0)
    {
        ll half = powMod(a, p / 2);
        return mulMod(half, half);
    }
    else
    {
        return mulMod(powMod(a, p - 1), a);
    }
}

ll ceil(ll a, ll b)
{
    return (a + b - 1) / b;
}

vector<ll> tsort(Graph G)
{
    ll N = G.size();
    vector<ll> in(N);
    for (auto &&edges : G)
    {
        for (auto &&edge : edges)
        {
            in[edge]++;
        }
    }

    queue<int> que;

    for (int i = 0; i < N; i++)
    {
        if (in[i] == 0)
        {
            que.push(i);
        }
    }
    int cnt = 0;
    vector<ll> ans;
    while (!que.empty())
    {
        int v = que.front();
        que.pop();
        ans.push_back(v);
        for (auto &&next : G[v])
        {

            in[next]--;
            if (in[next] == 0)
            {
                que.push(next);
            }
        }
    }
    return ans;
}

const int distX[4] = {-1, 0, 0, 1};
const int distY[4] = {0, 1, -1, 0};
int main()
{
    int H, W;
    cin >> H >> W;
    vector<string> map(H);
    for (int i = 0; i < H; i++)
    {
        string str;
        cin >> str;
        map[i] = str;
    }
    ll cnt = 0;
    for (int i = 0; i < H; i++)
    {
        for (int j = 0; j < W; j++)
        {
            if (map[i][j] == '.')
            {
                cnt++;
            }
        }
    }

    queue<pair<int, int>> que;
    vector<vector<ll>> dist(H, vector<ll>(W, -1));
    dist[0][0] = 0;

    que.push(make_pair(0, 0));

    while (!que.empty())
    {
        pair<int, int> p = que.front();
        int x = p.first;
        int y = p.second;
        que.pop();

        for (int i = 0; i < 4; i++)
        {
            int newX = x + distX[i];
            int newY = y + distY[i];
            if (newX < 0 || newX >= H || newY < 0 || newY >= W)
            {
                continue;
            }

            if (dist[newX][newY] != -1)
            {
                continue;
            }
            if (map[newX][newY] == '#')
            {
                continue;
            }
            dist[newX][newY] = dist[x][y] + 1;
            que.push(make_pair(newX, newY));
        }
    }

    if (dist[H - 1][W - 1] == -1)
    {
        cout << -1 << endl;
    }
    else
    {
        cout << cnt - dist[H - 1][W - 1] - 1 << endl;
    }
    return 0;
}


Measured memory_bytes: 256