#include <cstdio>
#include <cstdint>
#include <vector>
#include <string>
#include <queue>
#include <tuple>
#include <algorithm>
#include <utility>

constexpr size_t di[] = {size_t(-1), 0, 1, 0};
constexpr size_t dj[] = {0, size_t(-1), 0, 1};

int main() {
  size_t W, H;
  scanf("%zu %zu", &W, &H);

  std::vector<std::string> C(H);
  size_t si, sj;
  for (size_t i = 0; i < H; ++i) {
    char buf[32];
    scanf("%s", buf);
    C[i] = buf;
    for (size_t j = 0; j < W; ++j) {
      if (C[i][j] == '.') {
        si = i;
        sj = j;
      }
    }
  }

  std::queue<std::pair<size_t, size_t>> q;
  q.emplace(si, sj);
  while (!q.empty()) {
    size_t i, j;
    std::tie(i, j) = q.front();
    q.pop();
    if (C[i][j] != '.') continue;
    C[i][j] = ',';
    for (int k = 0; k < 4; ++k) {
      size_t ni = i + di[k];
      size_t nj = j + dj[k];
      if (!(ni < H && nj < W)) continue;
      if (C[ni][nj] != '.') continue;
      q.emplace(ni, nj);
    }
  }


  const int INF = 10000;
  std::vector<std::vector<int>> dp(H, std::vector<int>(W, INF));
  for (size_t i = 0; i < H; ++i)
    for (size_t j = 0; j < W; ++j)
      if (C[i][j] == ',') {
        q.emplace(i, j);
        dp[i][j] = 0;
      }

  while (!q.empty()) {
    size_t i, j;
    std::tie(i, j) = q.front();
    q.pop();
    if (C[i][j] == '.') continue;
    for (int k = 0; k < 4; ++k) {
      size_t ni = i + di[k];
      size_t nj = j + dj[k];
      if (!(ni < H && nj < W)) continue;
      if (dp[ni][nj] <= dp[i][j] + 1) continue;
      dp[ni][nj] = dp[i][j] + 1;
      q.emplace(ni, nj);
    }
  }

  int res = INF;
  for (size_t i = 0; i < H; ++i)
    for (size_t j = 0; j < W; ++j)
      if (C[i][j] == '.')
        res = std::min(res, dp[i][j]-1);

  printf("%d\n", res);
}