//#pragma GCC optimize("O3,unroll-loops,Ofast") //#pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt") #include <bits/stdc++.h> // #include <ext/pb_ds/assoc_container.hpp> // #include <ext/pb_ds/tree_policy.hpp> using namespace std; // using namespace __gnu_pbds; #define MAX 10005 #define pb push_back // #define mp make_pair #define int long long #define f first #define s second #define vi vector<int> #define pii pair<int,int> #define si set<int> #define vpii vector<pair<int,int>> const int mod = 1e9+7; const double INF = 1e18; // myMap.begin()->first : key // myMap.begin()->second : value int epow(int a,int b){int ans=1;while(b){if(b&1) ans*=a;a*=a;b>>=1;ans%=mod;a%=mod;}return ans%mod;} int gcd(int a,int b) {if(a<b)swap(a,b);while(b){int tmp=b;b=a%b;a=tmp;}return a;} int mul(int a,int b){return ((a%mod)*(b%mod))%mod;} int sum(int a,int b){return ((a%mod)+(b%mod))%mod;} //typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>ordered_set; // typedef // tree<int,null_type,less_equal<int>,rb_tree_tag,tree_order_statistics_node_update>ordered_multiset; int dx[]={1,0,-1,0}; int dy[]={0,1,0,-1}; int n,m; vector<vi> d(4005,vi(4005)); vector<vector<char>> grid(4005,vector<char>(4005)); bool valid(int a,int b){ if(a>0 && b>0 && a<=n && b<=m && grid[a][b]!='.') return true; return false; } void solve(){ cin>>n>>m; for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) cin>>grid[i][j]; deque<pii> q; q.push_back({1,1}); d[1][1]=1; while(q.size()){ pii node=q.front(); q.pop_front(); for(int i=0;i<4;i++){ int x=node.f+dx[i], y=node.s+dy[i]; if(!valid(x,y) || d[x][y]!=0 ) continue; d[x][y]=d[node.f][node.s]+(grid[node.f][node.s]!=grid[x][y]); if(grid[node.f][node.s]!=grid[x][y]) q.push_back({x,y}); else q.push_front({x,y}); } } int ans=1; for(int i=1;i<=n;i++) for(int j=1;j<=n;j++) ans=max(ans,d[i][j]); cout<<ans<<endl; } int32_t main(/*int32_t argc, char* argv[]*/){ std::ios_base::sync_with_stdio(0); std::cin.tie(0); // freopen("odometer.in", "r", stdin); // freopen("odometer.out", "w", stdout); int t=1; // cin >> t; while (t--) solve(); return 0; }