#ifdef __AVX2__
#pragma GCC target "avx2"
#endif
#pragma GCC optimize "O3"
#pragma GCC optimize "unroll-loops"
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
#define int long long
#define elif else if
#define all(l) begin(l),end(l)
#define rall(l) rbegin(l),rend(l)
#define append push_back
#define print(l) for(auto i:l) cout<<i<<' '; cout<<endl;
#define pprint(a,b) cout<<a<<' '<<b<<endl;
#define inp(l) for(auto &i:l) cin>>i;
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define pai make_pair
#define endl "\n"
#define pii pair<int,int>
#define fi first
#define se second
#define vec vector
// const int mod=998244353;
const int mod1=998244353;
const int mod=1e9+7;
const int N=4e3+5;
int n,m;
bool check(int x,int y){
return x>=0 and x<n and y>=0 and y<m;
}
void bfs(vec<string>s){
vec<vec<int>>dis(n+1,vec<int>(m+1,1e18));
dis[0][0]=1;
deque<pii>d;
d.append({0,0});
vec<int>dx={0,0,-1,1};
vec<int>dy={-1,1,0,0};
int ans=1;
while(d.size()){
int x=d[0].fi,y=d[0].se;
d.pop_front();
for(int j=0;j<4;j++){
int cx=x+dx[j],cy=y+dy[j];
if(check(cx,cy) and s[cx][cy]!='.' and dis[cx][cy]>1e9){
if(s[cx][cy]==s[x][y]){
dis[cx][cy]=dis[x][y];
d.push_front({cx,cy});
}
else{
dis[cx][cy]=dis[x][y]+1;
ans=dis[cx][cy];
d.append({cx,cy});
}
}
}
}
cout<<ans<<endl;
}
int iter=1,itera=1;
void solve(){
cin>>n>>m;
vec<string>s(n);
inp(s);
bfs(s);
}
signed main(){
// freopen("","r",stdin);
// freopen("","w",stdout);
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cout<<fixed<<setprecision(20);
// cin>>itera;
for(iter=1;iter<=itera;iter++) solve();
}
