#include <bits/stdc++.h>
using namespace std;

const int oo = 1000000010;
const int N = 100010;

const int dx[] = {1, -1, 0, 0}, dy[] = {0, 0, 1, -1};

int n, m, cost[510][510];
char arr[510][510];
bool vis[510][510];

int bfs1(){
    queue< pair<int, int> > q;
    q.push({0, 0});
    cost[0][0] = 0;
    vis[0][0] = true;
    while(!q.empty()){
        int x = q.front().first, y = q.front().second;
        q.pop();
        for(int i = 0; i < 4; ++i){
            int nx = x + dx[i], ny = y + dy[i];
            if(nx < 0 || nx >= n || ny < 0 || ny >= m){
                continue;
            }
            if(vis[nx][ny]){
                continue;
            }
            if(arr[nx][ny] == '#'){
                continue;
            }
            q.push({nx, ny});
            vis[nx][ny] = true;
            cost[nx][ny] = cost[x][y] + 1;
        }
    }
    return cost[n - 1][m - 1];
}

int bfs2(int xx, int yy, char c){
    memset(vis, false, sizeof(vis));
    queue< pair<int, int> > q;
    q.push({xx, yy});
    vis[xx][yy] = true;
    cost[xx][yy] = 0;
    int res = oo;
    while(!q.empty()){
        int x = q.front().first, y = q.front().second;
        q.pop();
        if(arr[x][y] == c){
            res = min(res, cost[x][y]);
        }
        for(int i = 0; i < 4; ++i){
            int nx = x + dx[i], ny = y + dy[i];
            if(nx < 0 || nx >= n || ny < 0 || ny >= m){
                continue;
            }
            if(vis[nx][ny]){
                continue;
            }
            if(arr[nx][ny] == '#'){
                continue;
            }
            q.push({nx, ny});
            vis[nx][ny] = true;
            cost[nx][ny] = cost[x][y] + 1;
        }
    }
    return res;
}

void solve(){
    cin >> n >> m;
    for(int i = 0; i < n; ++i){
        for(int j = 0; j < m; ++j){
            cin >> arr[i][j];
        }
    }
    memset(cost, -1, sizeof(cost));
    int ans = bfs1(), a, b;
    if(ans == -1){
        ans = oo;
    }
    a = bfs2(0, 0, 'O');
    b = bfs2(n - 1, m - 1, 'B');
    ans = min(ans, a + b + 1);
    a = bfs2(0, 0, 'B');
    b = bfs2(n - 1, m - 1, 'O');
    ans = min(ans, a + b + 1);
    cout << (ans < 2500 ? ans : -1);
}

int main(){
    int t = 1;
    //cin >> t;
    while(t--){
        solve();
    }
    return 0;
}