#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 = 1e11;

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;
}

bool isOK(map<char, ll> cnter, ll cnt, ll K, char c)
{
    if (cnt == K)
    {
        if (cnter[c] >= 1)
        {
            return true;
        }
        else
        {
            return false;
        }
    }
    else if (cnt == K - 1)
    {
        if (cnter[c] == 0)
        {
            return true;
        }
    }
    return false;
}
vector<ll> d(100);
vector<ll> f(100);

int dfs(Graph G, int v, int time)
{
    if (d[v] != 0)
        return time;
    d[v] = time;
    time++;
    for (int next_v : G[v])
    {
        if (d[next_v] != 0)
            continue;
        time = dfs(G, next_v, time);
    }

    f[v] = time;
    time++;
    return time;
}
ll dx[4] = {-1, 1, 0, 0};
ll dy[4] = {0, 0, 1, -1};
char field[100][100];
int dist[100][100];
int main()
{
    ll h, w;
    cin >> h >> w;
    ll cnt = 0;
    for (int i = 0; i < h; i++)
    {

        string str;
        cin >> str;
        for (int j = 0; j < w; j++)
        {
            field[i][j] = str[j];
            if (field[i][j] == '.')
                cnt++;
        }
    }

    memset(dist, -1, sizeof(dist));

    dist[0][0] = 1;
    queue<pair<int, int>> que;
    que.push(make_pair(0, 0));

    while (!que.empty())
    {
        auto q = que.front();
        que.pop();

        for (int k = 0; k < 4; k++)
        {
            int nx = q.first + dx[k];
            int ny = q.second + dy[k];

            if (nx < 0 || ny < 0 || nx >= h || ny >= w)
            {
                continue;
            }

            if (field[nx][ny] == '#')
            {
                continue;
            }
            if (dist[nx][ny] != -1)
            {
                continue;
            }

            dist[nx][ny] = dist[q.first][q.second] + 1;
            que.push(make_pair(nx, ny));
        }
    }
    if (dist[h - 1][w - 1] == -1)
    {
        cout << -1 << endl;
    }
    else
    {
        cout << cnt - dist[h - 1][w - 1] << endl;
    }
    return 0;
}


Measured memory_bytes: 256