#include<iostream>
#include<queue>
using namespace std;
char c[4010][4010];
int czy_odw[4010][4010];
pair<int,int>p[4]={{-1,0},{0,-1},{1,0},{0,1}};
int beefes(int a,int b){
int kt=1;
queue< pair<int,int> >q[2];
q[1].push({a,b});
czy_odw[a][b]=1;
while(!q[1].empty()){
while(!q[1].empty()){
q[0].push(q[1].front());
q[1].pop();
}
while(!q[0].empty()){
a=q[0].front().first;
b=q[0].front().second;
q[0].pop();
for(int i=0;i<4;i++){
int aa=a+p[i].first;
int bb=b+p[i].second;
if(czy_odw[aa][bb]==0&&c[aa][bb]!='.'){
czy_odw[aa][bb]=1;
q[(c[aa][bb]!=c[a][b])?1:0].push({aa,bb});
}
}
}
kt++;
}
return kt-1;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n,m;
cin>>n>>m;
for(int i=0;i<=n+1;i++){
for(int j=0;j<=m+1;j++){
if(i==0||j==0||i==n+1||j==m+1)c[i][j]='.';
else cin>>c[i][j];
}
}
cout<<beefes(1,1)<<'\n';
return 0;
}
