#include <bits/stdc++.h>
using namespace std;
#define int long long
vector<vector<char>> grid(4004,vector<char>(4004));
vector<vector<bool>> vis(4004,vector<bool>(4004,0));
vector<vector<int>> qat(4004,vector<int>(4004,0));
vector<int> dx = {1,0,-1,0};
vector<int> dy = {0,1,0,-1};
int n,m;
int cnt=0;
void dfs(int i,int j,int qat,queue<pair<int,int>> &yolla){
vis[i][j] = 1;
for(int ind =0;ind < 4;++ind){
int x = i + dx[ind];
int y = j + dy[ind];
if(x > n || x == 0 || y > m || y == 0)continue;
if(vis[x][y])continue;
if(grid[x][y] != grid[i][j]){
yolla.push({x,y});
}else dfs(x,y,qat,yolla);
}
}
signed main(){
int n,m;
cin >> n >> m;
bool f=0,r=0;
for(int i=1;i<=n;++i){
for(int j=1;j<=m;++j){
cin >> grid[i][j];
}
}
queue<pair<int,int>> nextt,nextt2,emptyy;
dfs(1,1,1,nextt);
int curr=2;
while(!nextt.empty()){
nextt2 = emptyy;
while(!nextt.empty()){
auto &[x,y] = nextt.front();
nextt.pop();
dfs(x,y,curr,nextt2);
}
nextt = nextt2;
curr++;
}
cout << curr;
}
