#include <bits/stdc++.h>
#define ll long long
using namespace std;
ll n, m, ans = 0;
vector<string> g;
vector<vector<ll>> dist;
vector<vector<bool>> vis;
void bfs(ll y, ll x){
deque<pair<ll, ll>> q;
q.push_back({y, x});
dist[y][x] = 1;
while(!q.empty()){
pair<ll, ll> val = q.front();
ll vy = val.first, vx = val.second;
q.pop_front();
if(vis[vy][vx]) continue;
for(ll dy = (vy > 0 ? -1 : 0); dy <= (vy < n-1 ? 1 : 0); dy++){
if(g[vy+dy][vx] != '.' && vis[vy+dy][vx] == false){
if(g[vy][vx] == g[vy+dy][vx]){
q.push_front({vy+dy, vx});
dist[vy+dy][vx] = dist[vy][vx];
}
else{
q.push_back({vy+dy, vx});
dist[vy+dy][vx] = dist[vy][vx] + 1;
}
}
}
for(ll dx = (vx > 0 ? -1 : 0); dx <= (vx < m-1 ? 1 : 0); dx++){
if(g[vy][vx+dx] != '.' && vis[vy][vx+dx] == false){
if(g[vy][vx] == g[vy][vx+dx]){
q.push_front({vy, vx+dx});
dist[vy][vx+dx] = dist[vy][vx];
}
else{
q.push_back({vy, vx+dx});
dist[vy][vx+dx] = dist[vy][vx] + 1;
}
}
}
vis[vy][vx] = true;
ans = dist[vy][vx];
}
}
int main(){
cin >> n >> m;
g.resize(n), dist.resize(n), vis.resize(n);
for(ll i = 0; i < n; i++){
cin >> g[i];
dist[i].assign(m, -1);
vis[i].assign(m, false);
}
bfs(0, 0);
cout << ans << "\n";
}
