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


bool isValid(int x,int y,vector<vector<char>>& mat,vector<vector<bool>>& visited){
  int n = mat.size();
  int m = mat[0].size();
  
  if(x >= n or y>=m or x<0 or y<0 or mat[x][y]=='#' or vis[x][y]){
    return false;
  }
  return true;
}

vector<pair<int,int>> cords = {
  {1,0},{0,1},{-1,0},{0,-1}
};


int funcTion(vector<vector<char>>& mat){
  int n = mat.size();
  int m = mat[0].size();
  
  pair<int,int>B_initial = {-1,-1}; // initialization
  pair<int,int>B_final = {-1,-1};
  
  pair<int,int> O_initial = {-1,-1};
  pair<int,int> O_final = {-1,-1};
  
  for(int i=0;i<n;i++) for(int j=0;j<m;j++){
    if(mat[i][j] == 'B'){
      if(B_initial.first != -1 and B_initial.second != -1){
        B_final.first = i;
        B_final.second = j;
      } 
      else{
        B_initial.first = i;
        B_initial.second = j;
      }
    } // cords. of the B
    
    
    if(O_initial.first != -1 and O_initial.second != -1){
        O_final.first = i;
        O_final.second = j;
      } 
      else{
        O_initial.first = i;
        O_initial.second = j;
      }
    } // cords. of the O 
  
  
  if(mat[0][0] =='#' or mat[n-1][m-1] == '#'){
    return -1;
  } // already the cell is blocked
  
  vector<vector<bool>> visited(n,vector<bool>(m,false));
  queue<tuple<int,int,int>> q;
  
  q.push({0,0,0});
  visited[0][0] = true;
  
  while(!q.empty()){
    int sz = q.size();
    while(sz--){
      tuple current = q.front(); q.pop();
      
      int x = get<0>(current);
      int y = get<1>(current);
      int d = get<2>(current);
      
      if(x == n-1 and y == m-1 and mat[x][y] == '.'){
        return d;
      }
      
      for(auto [dx,dy]:cords){
        if(isValid(x+dx,y+dy,mat,visited)){
          if(mat[x+dx][y+dy] == 'B' or (x+dx == B_initial.first and y+dy == B_initial.second)){
            q.push({B_final.first,B_final.second,d+1});
            visited[B_final.first][B_final.second] = true;
          }
        }
        
        else if(isValid(x+dx,y+dy,mat,visited)){
          if(mat[x+dx][y+dy] == 'O' or (x+dx == O_initial.first and y+dy == O_initial.second)){
            q.push({O_final.first,O_final.second,d+1});
            visited[O_final.first][O_final.second] = true;
          }
        }
        else{
           q.push({x+dx,y+dy,d+1});
           visited[x+dx][y+dy] = true;
        }
      }
    }
  }
  return -1;
}

void solve(){
  int n,m;
  cin>>n>>m;
  
  vector<vector<char>>mat(n,vector<char>(m));
  for(int i=0;i<n;i++){
    for(int j=0;j<m;j++){
      cin>> mat[i][j];
    }
  }
  cout << funcTion(mat);
  return;
}
signed main(){
  ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    
    solve();
    return 0;
}