#include <deque>
#include <iostream>
#include <vector>
using namespace std;
/*
Input:
H : int [1, 4000]
W : int [1, 4000]
`map` :
. -> untouched
R -> rabit
F -> fox
Rules:
1. Each animal starts at (0,0) moves along xy axes
2. Each new animal footprint replaces old one
........ RRR..... FFR.....
........ ..RRR... .FRRR...
........ ..R..... .FFFFF..
........ ..RRRR.R ..RRRFFR
........ .....RRR .....FFF
RFR.....
.FRRR...
.FFFFF..
*/
int rows[] = {-1, 1, 0, 0};
int cols[] = {0, 0, -1, 1};
struct point {
int r, c, distance;
point(int r, int c) : r(r), c(c) {}
point(int r, int c, int distance) : r(r), c(c) , distance(distance) {}
};
void bfs(const vector<string> &tracks) {
point start(0,0,0);
deque<point> bfs_queue;
vector<vector<bool>> visited(tracks.size(), vector(tracks[0].size(), false));
bfs_queue.push_front(start);
int max_animals = 0;
while(!bfs_queue.empty()) {
point shortest_point_so_far = bfs_queue.front();
bfs_queue.pop_front();
int r = shortest_point_so_far.r , c = shortest_point_so_far.c, distance = shortest_point_so_far.distance;
visited[shortest_point_so_far.r][shortest_point_so_far.c] = true;
max_animals = max(max_animals, distance);
for(int i = 0 ; i < 4; ++i) {
int nr = r + rows[i];
int nc = c + cols[i];
if (nr < 0 || nc <0 || nr >= tracks.size() || nc >= tracks[0].size()) {
continue;
}
if(tracks[nr][nc] == '.') continue;
if(visited[nr][nc]) continue;
if(tracks[nr][nc] != tracks[r][c]) {
bfs_queue.push_back(point(nr, nc, distance + 1));
} else {
bfs_queue.push_front(point(nr, nc, distance));
}
}
}
cout << max_animals + 1 << "\n";
}
int main() {
int h, w;
cin >> h >> w;
vector<string> tracks(h);
for (int i = 0; i < h; ++i) {
cin >> tracks[i];
}
bfs(tracks);
}
