#include <bits/stdc++.h>

template <typename T>
class Grid {
  template <typename U>
  using pqueue = std::priority_queue<U, std::vector<U>, std::greater<U>>;

 public:
  Grid(int height, int width) : grid_(height, std::vector<T>(width)) {}
  void Set(int row, int col, T value) { grid_[row][col] = value; }
  std::optional<T> Distance(int src_row, int src_col, int dst_row,
                            int dst_col) {
    if (grid_[src_row][src_col] < 0) {
      return std::nullopt;
    }
    pqueue<std::tuple<T, int, int>> que;
    que.push({0, src_row, src_col});
    std::map<std::pair<int, int>, T> visited;
    visited[{src_row, src_col}] = 0;
    while (!que.empty()) {
      auto [dist, row, col] = que.top();
      que.pop();
      if (row == dst_row && col == dst_col) {
        return dist;
      }
      int dr[] = {1, -1, 0, 0};
      int dc[] = {0, 0, 1, -1};
      for (int i = 0; i < 4; ++i) {
        int nrow = row + dr[i];
        int ncol = col + dc[i];
        if (nrow < 0 || grid_.size() <= nrow || ncol < 0 ||
            grid_[0].size() <= ncol || grid_[nrow][ncol] < 0) {
          continue;
        }
        int ndist = dist + grid_[nrow][ncol];
        const auto it = visited.find({nrow, ncol});
        if (it != visited.end() && it->second <= ndist) {
          continue;
        }
        visited[{nrow, ncol}] = ndist;
        que.push({ndist, nrow, ncol});
      }
    }
    return std::nullopt;
  }

 private:
  std::vector<std::vector<T>> grid_;
};

template <typename T, typename _ = void>
struct is_container : std::false_type {};
template <typename T>
struct is_container<T, std::void_t<decltype(std::declval<T>().begin()),
                                   decltype(std::declval<T>().end())>>
    : std::true_type {};
template <typename T, typename _ = void>
struct is_pair : std::false_type {};
template <typename T>
struct is_pair<T, std::void_t<decltype(std::declval<T>().first),
                              decltype(std::declval<T>().second)>>
    : std::true_type {};
template <typename T>
void debug(const T& v) {
  if constexpr (is_pair<T>::value) {
    std::cerr << "{";
    debug(v.first);
    std::cerr << ", ";
    debug(v.second);
    std::cerr << "}";
  } else if constexpr (is_container<T>::value) {
    std::cerr << "{";
    for (auto it = v.begin(); it != v.end(); ++it) {
      if (it != v.begin()) std::cerr << ", ";
      debug(*it);
    }
    std::cerr << "}";
  } else {
    std::cerr << v;
  }
}
template <typename T, typename... Ts>
void debug(const T& value, const Ts&... args) {
  debug(value);
  std::cerr << ", ";
  debug(args...);
}
#if DEBUG
#define dbg(...)                        \
  do {                                  \
    cerr << #__VA_ARGS__ << ": ";       \
    debug(__VA_ARGS__);                 \
    cerr << " (L" << __LINE__ << ")\n"; \
  } while (0)
#else
#define dbg(...)
#endif

void read_from_cin() {}
template <typename T, typename... Ts>
void read_from_cin(T& value, Ts&... args) {
  std::cin >> value;
  read_from_cin(args...);
}
#define rd(type, ...) \
  type __VA_ARGS__;   \
  read_from_cin(__VA_ARGS__);

template <typename T>
void write_to_cout(const T& value) {
  if constexpr (std::is_same<T, bool>::value) {
    std::cout << (value ? "Yes" : "No");
  } else {
    std::cout << value;
  }
}
template <typename T, typename... Ts>
void write_to_cout(const T& value, const Ts&... args) {
  write_to_cout(value);
  std::cout << ' ';
  write_to_cout(args...);
}
#define wt(...)                 \
  do {                          \
    write_to_cout(__VA_ARGS__); \
    cout << '\n';               \
  } while (0)

#define all(x) (x).begin(), (x).end()
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; --i)

template <typename T>
std::istream& operator>>(std::istream& is, std::vector<T>& v) {
  for (T& vi : v) is >> vi;
  return is;
}

template <typename T, typename U>
bool chmax(T& a, U b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

template <typename T, typename U>
bool chmin(T& a, U b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

#include <boost/hana/functional/fix.hpp>
auto Fix = boost::hana::fix;

using ll = long long;

template <typename T>
using low_priority_queue =
    std::priority_queue<T, std::vector<T>, std::greater<T>>;

template <typename T>
using V = std::vector<T>;
template <typename T>
using VV = V<V<T>>;

using namespace std;

int main() {
  rd(int, h, w);
  V<string> s(h);
  cin >> s;

  Grid<int> g(h, w);
  rep(i, h) rep(j, w) g.Set(i, j, (s[i][j] == '#' ? -1 : 1));
  optional<int> d = g.Distance(0, 0, h - 1, w - 1);
  if (!d) {
    wt(-1);
  } else {
    int black = 0;
    rep(i, h) black += count(all(s[i]), '#');
    wt(h * w - black - *d - 1);
  }
}


Measured memory_bytes: 3724