#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<iomanip>
#include<cmath>
#include<set>
#include<queue>

using namespace std;

vector<vector<bool>> used;
vector<vector<char>> a;
vector<pair<int, int>> v = { {0, 1}, {1, 0}, {-1, 0}, {0, -1} };
int r, c;
vector<vector<int>> vec;
int it = 0;

void dfs(int x, int y) {
	used[x][y] = 1;
	vec[x][y] = it;
	for (auto u : v) {
		int nx = x + u.first;
		int ny = y + u.second;
		if (0 <= nx && nx < r && 0 <= ny && ny < c && !used[nx][ny] && a[nx][ny] == 'X') {
			dfs(nx, ny);
		}
	}
}

signed main()
{
	cin >> r >> c;
	used.resize(r, vector<bool>(c));
	a.resize(r, vector<char>(c));
	vec.resize(r, vector<int>(c));
	for (int i = 0; i < r; i++) {
		for (int j = 0; j < c; j++) {
			cin >> a[i][j];
		}
	}
	for (int i = 0; i < r; i++) {
		for (int j = 0; j < c; j++) {
			if (!used[i][j] && a[i][j] == 'X') {
				dfs(i, j);
				it++;
			}
		}
	}
	vector<vector<pair<int, int>>> g(it);
	for (int i = 0; i < r; i++) {
		for (int j = 0; j < c; j++) {
			if (a[i][j] == 'X') {
				g[vec[i][j]].push_back({ i, j });
			}
		}
	}
	vector<vector<int>> f(it, vector<int>(it, 1e9));
	for (int i = 0; i < it; i++) {
		f[i][i] = 0;
	}
	for (int i = 0; i < it; i++) {
		vector<vector<int>> dist(r, vector<int>(c, 1e9));
		queue<pair<int, int>> q;
		for (auto j : g[i]) {
			dist[j.first][j.second] = 0;
			q.push(j);
		}
		while (!q.empty()) {
			auto s = q.front();
			q.pop();
			for (int j = 0; j < 4; j++) {
				int nx = s.first + v[j].first;
				int ny = s.second + v[j].second;
				if (0 <= ny && ny < c && 0 <= nx && nx < r && a[nx][ny] != '.' && dist[nx][ny] > dist[s.first][s.second] + 1) {
					dist[nx][ny] = dist[s.first][s.second] + 1;
					q.push({ nx, ny });
					if (a[nx][ny] == 'X' && vec[nx][ny] != vec[s.first][s.second]) {
						f[i][vec[nx][ny]] = min(f[i][vec[nx][ny]], dist[nx][ny] - 1);
					}
				}
			}
		}
	}
	vector<vector<int>> dp((1 << it), vector<int>((1 << it), 1e9));
	for (int i = 0; i < it; i++) {
		dp[(1 << i)][i] = 0;
	}
	for (int mask = 1; mask < (1 << it); mask++) {
		for (int last = 0; last < it; last++) {
			if (!((1 << last) & mask)) {
				continue;
			}
			for (int i = 0; i < it; i++) {
				if ((mask >> i) & 1) {
					dp[mask][last] = min(dp[mask][last], dp[mask - (1 << last)][i] + f[last][i]);
				}
			}
		}
	}
	int ans = 1e9;
	for (int i = 0; i < it; i++) {
		ans = min(ans, dp[(1 << it) - 1][i]);
	}
	cout << ans;
}