#include<bits/stdc++.h>
using namespace std;
#define int long long
#define gcd __gcd
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
int n,m,ans1=0,ans2=0;
cin>>n>>m;
vector<array<int,2>>vc[n+5][m+5];
string s[n+5];
int vs[n+5][m+5]={};
for(int x=0;x<n;x++)cin>>s[x];
bool b=0,t=0;
for(int x=0;x<n;x++)for(int y=0;y<m;y++)
{
if(s[x][y]=='B')b=1;
if(s[x][y]=='T')t=1;
if(x!=n-1&&s[x+1][y]==s[x][y])
{
vc[x][y].push_back({x+1,y});
vc[x+1][y].push_back({x,y});
}
if(y!=m-1&&s[x][y+1]==s[x][y])
{
vc[x][y].push_back({x,y+1});
vc[x][y+1].push_back({x,y});
}
}
for(int x=0;x<n;x++)for(int y=0;y<m;y++)if(!vs[x][y]&&s[x][y]=='T')
{
ans1++;
queue<array<int,2>>q;
q.push({x,y});
while(q.size())
{
auto [X,Y]=q.front();
q.pop();
if(vs[X][Y])continue;
vs[X][Y]=1;
for(auto [i,j]:vc[X][Y])if(!vs[i][j])q.push({i,j});
}
}
for(int x=0;x<n;x++)for(int y=0;y<m;y++)if(!vs[x][y]&&s[x][y]=='B')
{
ans2++;
queue<array<int,2>>q;
q.push({x,y});
while(q.size())
{
auto [X,Y]=q.front();
q.pop();
if(vs[X][Y])continue;
vs[X][Y]=1;
for(auto [i,j]:vc[X][Y])if(!vs[i][j])q.push({i,j});
}
}
cout<<min(ans1+(s[0][0]=='B')+b,ans2+(s[0][0]=='T')+t)<<endl;
}
