#include <iostream>
#include <vector>
#include <queue>
#include <map>
#include <climits>
#include <algorithm>
using namespace std;

bool lehet(pair<int,int> pos,vector<vector<char>> &adj,int &n,int &m)
{
if(pos.first<0 || pos.first>=n || pos.second<0 || pos.second>=m)return false;
return true;
}

int main()
{
    int n,m;
    cin>>n>>m;
    vector<vector<char>> adj(n,vector<char> (m));
    pair<int,int> posA,posB;
    for(int i=0;i<n;i++)
        {
        for(int j=0;j<m;j++)
            {
            cin>>adj[i][j];
            if(adj[i][j]=='A')posA={i,j};
            if(adj[i][j]=='B')posB={i,j};
            }
        }
    queue<pair<int,int>> q;
    q.push(posA);

    vector<vector<bool>> vis(n,vector<bool> (m,false));
    vis[posA.first][posA.second]=true;
    queue<pair<int,int>> q2;
    vector<vector<int>> dist(n,vector<int> (m,INT_MAX));
    vector<vector<bool>> vis2(n,vector<bool> (m,false));
    while(q.size())
        {
        dist[q.front().first][q.front().second]=0;
        q2.push(q.front());
        vis2[q.front().first][q.front().second]=true;
        auto [x,y]=q.front();q.pop();

        if(x==posB.first && y==posB.second)
            {
            cout<<0;
            return 0;
            }
        if(lehet({x-1,y},adj,n,m) && adj[x-1][y]!='#' && !vis[x-1][y])
            {
            vis[x-1][y]=true;
            q.push({x-1,y});
            }
        if(lehet({x+1,y},adj,n,m) && adj[x+1][y]!='#' &&!vis[x+1][y] )
            {
            vis[x+1][y]=true;
            q.push({x+1,y});
            }
        if(lehet({x,y-1},adj,n,m) && adj[x][y-1]!='#' && !vis[x][y-1] )
            {
            vis[x][y-1]=true;
            q.push({x,y-1});
            }
        if(lehet({x,y+1},adj,n,m)  &&!vis[x][y+1] && adj[x][y+1]!='#')
            {
            vis[x][y+1]=true;
            q.push({x,y+1});
            }
        }
    while(q2.size())
        {
        auto [x,y]=q2.front();q2.pop();
        if( lehet({x-1,y},adj,n,m) && !vis2[x-1][y] )
            {
            vis2[x-1][y]=true;
            q2.push({x-1,y});
            dist[x-1][y]=min(dist[x-1][y],dist[x][y]+1);
            }
        if(lehet({x+1,y},adj,n,m) &&!vis2[x+1][y]  )
            {
            vis2[x+1][y]=true;
            q2.push({x+1,y});
            dist[x+1][y]=min(dist[x+1][y],dist[x][y]+1);
            }
        if(lehet({x,y-1},adj,n,m)&&!vis2[x][y-1] )
            {
            vis2[x][y-1]=true;
            q2.push({x,y-1});
            dist[x][y-1]=min(dist[x][y-1],dist[x][y]+1);
            }
        if(lehet({x,y+1},adj,n,m) && !vis2[x][y+1] )
            {
            vis2[x][y+1]=true;
            q2.push({x,y+1});
            dist[x][y+1]=min(dist[x][y+1],dist[x][y]+1);
            }
        }
    int ans=dist[posB.first][posB.second];
    while(q.size())q.pop();
    fill(vis.begin(),vis.end(),vector<bool> (m,false));
    q.push(posB);
    vis[posB.first][posB.second]=true;
    while(q.size())
        {
        auto [x,y]=q.front();q.pop();
        if(lehet({x-1,y},adj,n,m)&& !vis[x-1][y]  && adj[x-1][y]!='#')
            {
            vis[x-1][y]=true;
            q.push({x-1,y});
            ans=min(ans,dist[x-1][y]);
            }
        if(lehet({x+1,y},adj,n,m) && !vis[x+1][y] && adj[x+1][y]!='#')
            {
            vis[x+1][y]=true;
            q.push({x+1,y});
            ans=min(ans,dist[x+1][y]);
            }
        if(lehet({x,y-1},adj,n,m) && !vis[x][y-1] && adj[x][y-1]!='#')
            {
            vis[x][y-1]=true;
            q.push({x,y-1});
            ans=min(ans,dist[x][y-1]);
            }
        if(lehet({x,y+1},adj,n,m) && !vis[x][y+1] && adj[x][y+1]!='#')
            {
            vis[x][y+1]=true;
            q.push({x,y+1});
            ans=min(ans,dist[x][y+1]);
            }
        }
    cout<<ans;
    return 0;
}