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

int n, m;
vector<vector<char>>g;
vector<vector<bool>>vis;

void dfs(int i, int j)
{
    if(i < 0 || i >= n || j < 0 || j >= m || vis[i][j] || g[i][j] == '#') return;
    vis[i][j] = 1;
    dfs(i+1, j);
    dfs(i-1, j);
    dfs(i, j+1);
    dfs(i, j-1);
}

signed main() {
    ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
    cin >> n >> m;
    g.resize(n, vector<char>(m)); vis.resize(n, vector<bool>(m));
    pair<int, int>a, b;
    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < m; j++)
        {
            cin >> g[i][j];
            if(g[i][j] == 'A') a = {i, j};
            if(g[i][j] == 'B') b = {i, j};
        }
    }
    dfs(a.first, a.second);
    if(vis[b.first][b.second]) {cout << 0; return 0;}
    queue<pair<int, int>>q;
    vector<vector<int>>dist(n, vector<int>(m, -1));
    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < m; j++)
        {
            if(vis[i][j])
            {
                dist[i][j] = 0;
                q.push({i, j});
            }
        }
    }
    int ans = 4000;
    dfs(b.first, b.second);
    while(!q.empty())
    {
        auto [i, j] = q.front();
        q.pop();
        if(dist[i][j] != 0 && vis[i][j]) ans = min(ans, dist[i][j]);
        if(i > 0 && dist[i-1][j] == -1) {dist[i-1][j] = dist[i][j] + 1; q.push({i-1, j});}
        if(i < n-1 && dist[i+1][j] == -1) {dist[i+1][j] = dist[i][j] + 1; q.push({i+1, j});}
        if(j > 0 && dist[i][j-1] == -1) {dist[i][j-1] = dist[i][j] + 1; q.push({i, j-1});}
        if(j < m-1 && dist[i][j+1] == -1) {dist[i][j+1] = dist[i][j] + 1; q.push({i, j+1});}
    }
    cout << ans;
}