#include <bits/stdc++.h>
#define int long long
using namespace std;
typedef vector<int> vi;
typedef pair<int, int> ii;
int n, m;
vector<vector<char>> mtx;
vector<vector<int>> depth;
deque<ii> q;
// dr, dc, mov
tuple<int, int, char> moves[]{{1, 0, 'D'}, {-1, 0, 'U'}, {0, 1, 'R'}, {0, -1, 'L'}};
bool is_possible(ii pos){
auto [r, c] = pos;
if(r < 0 || r >= n || c < 0 || c >= m) return false;
return true;
}
int bfs(ii src){
int qtt = 1;
q.emplace_back(src);
while(!q.empty()){
ii curr = q.back();
q.pop_back();
qtt = max(qtt, depth[curr.first][curr.second]);
for(auto [dr, dc, mov] : moves){
int new_r = curr.first + dr;
int new_c = curr.second + dc;
if(is_possible({new_r, new_c})){
if(depth[new_r][new_c] != 0) continue;
if(mtx[new_r][new_c] == '.') continue;
if(mtx[new_r][new_c] == mtx[curr.first][curr.second]){
depth[new_r][new_c] = depth[curr.first][curr.second];
q.emplace_back(new_r, new_c);
}
else{
depth[new_r][new_c] = depth[curr.first][curr.second] + 1;
q.emplace_front(new_r, new_c);
}
}
}
}
return qtt;
}
void solve(){
// int n, m;
cin >> n >> m;
vector<ii> cands;
mtx.assign(n, vector<char>(m));
depth.assign(n, vector<int>(m, 0));
for(int i=0; i<n; i++){
for(int j=0; j<m; j++){
cin >> mtx[i][j];
}
}
depth[0][0] = 1;
int ans = bfs({0, 0});
cout << ans << "\n";
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
solve();
return 0;
}
