/*#pragma GCC target ("avx2")
#pragma GCC optimize ("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")*/
#include<bits/stdc++.h>
/*#include <bits/extc++.h>
using namespace std;
using namespace __gnu_pbds;
template<class T>
using oset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
/**/
//typedef int ll;
typedef long long ll;
typedef unsigned long long ull;
typedef __int128 vll;
typedef unsigned __int128 uvll;
ll _i=0;
#define ffn(x) _i=x
#define llll std::pair<ll , ll>
#define stitr set<ll>::iterator
#define fora(y,x) for(ll y=_i;x>y;y++)
#define pb push_back
#define pf push_front
#define halo cout << "hello\n"
#define fi first
#define sec second
#define all(a) a.begin() , a.end()
const ll limit = 1e9 + 7;
const ll ous = 1e6 + 7;
const ll dx[4] = {1 , 0 , 0 , -1} , dy[4] = {0,1,-1,0};
void solve(){
ll n , m;std::cin >> n >> m;
ll vis[n+5][m+5];
memset(vis , 0 , sizeof(vis));
std::string h[n];
fora(i , n){
std::cin >> h[i];
}
std::vector<llll> v;
v.pb({0 , 0});
std::queue<llll> que;
ll ans = 0;
while(!v.empty()){
for(auto j:v){
que.push(j);
}
v.clear();
while(!que.empty()){
llll a = que.front();
que.pop();
if(vis[a.fi][a.sec] == 2){
continue;
}
vis[a.fi][a.sec] = 2;
fora(i , 4){
if(dx[i] + a.fi >= 0 && dx[i] + a.fi < n && dy[i] + a.sec >= 0 && dy[i] + a.sec < m && h[dx[i] + a.fi][dy[i] + a.sec] != '.'){
if(h[dx[i] + a.fi][dy[i] + a.sec] == h[a.fi][a.sec] && vis[dx[i] + a.fi][dy[i] + a.sec] == 0){
vis[dx[i] + a.fi][dy[i] + a.sec] = 1;
que.push({dx[i] + a.fi , dy[i] + a.sec});
}
else if(vis[dx[i] + a.fi][dy[i] + a.sec] == 0){
vis[dx[i] + a.fi][dy[i] + a.sec] = 1;
v.pb({dx[i] + a.fi , dy[i] + a.sec});
}
}
}
}
ans++;
}
std::cout << ans << "\n";
return;/**/
}
signed main(){
std::ios_base::sync_with_stdio(false);std::cin.tie(NULL);
ll t=1;
//std::cin >> t;
ll o = 1;
while(t--){
//cout << "Case " << o++ << ":\n";
solve();
}
return 0;
}
