/*
*
* ^v^
*
*/
#include <iostream>
#include <string>
#include <cmath>
#include <vector>
#include <iomanip>
#include <map>
#include <numeric>
#include <functional>
#include <algorithm>
#include <set>
#include <queue>
#include <deque>
#include <climits>
#include <cstdlib>
#include <chrono>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
using namespace std;
// #define ordered_set tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update>
#define iamtefu ios_base::sync_with_stdio(false); cin.tie(0);
#define ll int
#define ld long double
#define sc(a) scanf("%lld", &a);
#define scv(a, n) vector<ll> a(n);fl(i,0,n){sc(a[i])}
#define prl(a) fl(i,0,a.size()){printf("%lld ", a[i]);}printf("\n");
#define fl(i,a,n) for (ll i(a); i<n; i++)
#define rfl(i,a,n) for (ll i(n-1); i>=a; i--)
#define print(a) for (auto x:a){cout<<x<<" ";} cout<<"\n";
#define tt int tt; cin>>tt; for(;tt--;)
ll gcd(ll a, ll b){
if (b==0){
return a;
}
return gcd(b, a%b);
}
ll pw(ll a, ll b, ll m){
ll res=1;
a%=m;
while (b){
if (b&1){
res=(res*a)%m;
}
a=(a*a)%m;
b/=2;
}
return res;
}
void scn(){
ll n, m; cin>>n>>m;
vector <string> a(n+1);
fl(i,0,n){
cin>>a[i];
}
vector <ll> di={1, 1, 0, -1, -1, -1, 0, 1};
vector <ll> dj={0, 1, 1, 1, 0, -1, -1, -1};
vector <vector <ll>> dis(n, vector <ll>(m, 0));
dis[0][0] = 1;
ll ans = 0;
deque <pair<ll,ll>> q;
q.push_back({0, 0});
while (!q.empty()){
auto j = q.front();
q.pop_front();
ans = max(ans, dis[j.first][j.second]);
// cerr<<j.first<<" "<<j.second<<'\n';
for (int d = 0; d<8; d+=2){
ll i1 = j.first+di[d], j1 = j.second+dj[d];
if (i1<0 || i1>=n || j1<0 || j1>=m || a[i1][j1]=='.' || dis[i1][j1]){
continue;
} else {
dis[i1][j1] = dis[j.first][j.second]+(a[j.first][j.second]!=a[i1][j1]);
if (a[j.first][j.second]==a[i1][j1]){
q.push_front({i1, j1});
} else {
q.push_back({i1, j1});
}
}
}
}
cout<<ans<<'\n';
// not necessarily distinct
}
int main(){
iamtefu;
#if defined(airths)
auto t1=chrono::high_resolution_clock::now();
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#else
//
#endif
// tt
{
scn();
}
#if defined(airths)
auto t2=chrono::high_resolution_clock::now();
ld ti=chrono::duration_cast<chrono::nanoseconds>(t2-t1).count();
ti*=1e-6;
cerr<<"Time: "<<setprecision(12)<<ti;
cerr<<"ms\n";
#endif
return 0;
}
