#include <iostream>
#include <queue>
#include <cstring>
#include <climits>
using namespace std;

#define MAX 55

char g[MAX][MAX];
int n, m;
int dx[] = {-1, 1, 0, 0};
int dy[] = {0, 0, -1, 1};

// 标记岛屿
void markIsland(int x, int y, char mark) {
    queue<pair<int, int>> q;
    q.push({x, y});
    g[x][y] = mark;
    
    while (!q.empty()) {
        int cx = q.front().first;
        int cy = q.front().second;
        q.pop();
        
        for (int i = 0; i < 4; i++) {
            int nx = cx + dx[i];
            int ny = cy + dy[i];
            
            if (nx >= 0 && nx < n && ny >= 0 && ny < m && g[nx][ny] == 'X') {
                g[nx][ny] = mark;
                q.push({nx, ny});
            }
        }
    }
}

// 计算两个岛屿之间的最短距离
int findShortestPath() {
    // dist数组记录从第一个岛屿到每个位置的距离
    int dist[MAX][MAX];
    memset(dist, -1, sizeof(dist));
    
    queue<pair<int, int>> q;
    
    // 将所有第一个岛屿的点加入队列
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            if (g[i][j] == 'A') {
                dist[i][j] = 0;
                q.push({i, j});
            }
        }
    }
    
    while (!q.empty()) {
        int x = q.front().first;
        int y = q.front().second;
        q.pop();
        
        // 如果到达第二个岛屿，返回距离-1（因为最后一个格子是陆地，不需要填充）
        if (g[x][y] == 'B') {
            return dist[x][y] - 1;
        }
        
        for (int i = 0; i < 4; i++) {
            int nx = x + dx[i];
            int ny = y + dy[i];
            
            if (nx >= 0 && nx < n && ny >= 0 && ny < m && dist[nx][ny] == -1) {
                // 可以走海水或者第二个岛屿
                if (g[nx][ny] == '.' || g[nx][ny] == 'B') {
                    dist[nx][ny] = dist[x][y] + 1;
                    q.push({nx, ny});
                }
            }
        }
    }
    
    return INT_MAX; // 理论上不会执行到这里
}

int main() {
    cin >> n >> m;
    
    for (int i = 0; i < n; i++) {
        cin >> g[i];
    }
    
    // 标记第一个岛屿为'A'
    bool foundFirst = false;
    for (int i = 0; i < n && !foundFirst; i++) {
        for (int j = 0; j < m && !foundFirst; j++) {
            if (g[i][j] == 'X') {
                markIsland(i, j, 'A');
                foundFirst = true;
            }
        }
    }
    
    // 标记第二个岛屿为'B'
    bool foundSecond = false;
    for (int i = 0; i < n && !foundSecond; i++) {
        for (int j = 0; j < m && !foundSecond; j++) {
            if (g[i][j] == 'X') {
                markIsland(i, j, 'B');
                foundSecond = true;
            }
        }
    }
    
    int result = findShortestPath();
    cout << result << endl;
    
    return 0;
}