#include <bits/stdc++.h>
using namespace std;
const int nx=1e3+5;
int n, m, di[4]={1, 0, 0, -1}, dj[4]={0, 1, -1, 0}, c[100], cur, ans, vs[nx][nx];
char mp[nx][nx];
int main()
{
cin.tie(NULL)->sync_with_stdio(false);
cin>>n>>m;
for (int i=1 ;i<=n; i++) for (int j=1; j<=m; j++) cin>>mp[i][j];
c['T']=0;
c['B']=1;
cur=c[mp[1][1]];
queue<pair<int, int>> q, nq;
vs[1][1]=1;
q.push({1, 1});
while (!q.empty())
{
ans++;
while (!q.empty())
{
auto [i, j]=q.front();
q.pop();
for (int k=0; k<4; k++)
{
int ni=i+di[k], nj=j+dj[k];
if (vs[ni][nj]) continue;
vs[ni][nj]=1;
if (mp[ni][nj]!='B'&&mp[ni][nj]!='T') continue;
if (c[mp[ni][nj]]==cur) q.push({ni, nj});
if (c[mp[ni][nj]]==!cur) nq.push({ni, nj});
}
}
cur=!cur;
//cout<<"debug "<<nq.size()<<'\n';
q=nq;
while (!nq.empty()) nq.pop();
}
cout<<ans;
}
