// #include <bits/stdc++.h>
// using namespace std;
// int H,W;
// void dfs(int r,int c,vector<vector<int>>& matrix,vector<vector<int>>& minDist){
// // cout << r << " " << c << endl;
// int dx[4] = {0,1,-1,0};
// int dy[4] = {1,0,0,-1};
// for(int i = 0;i < 4;i++){
// int newX = r+dx[i];
// int newY = c+dy[i];
// if(newX < 0 || newY < 0 || newX >= H || newY >= W){
// continue;
// }
// if(matrix[newX][newY] == 0)continue;
// int newDist = minDist[r][c];
// if(matrix[newX][newY] != matrix[r][c]){
// newDist++;
// }
// if(minDist[newX][newY] > newDist){
// minDist[newX][newY] = newDist;
// dfs(newX,newY,matrix,minDist);
// }
// }
// }
// int main(){
// cin.tie(0);
// ios_base::sync_with_stdio(0);
// //start here
//
// cin >> H >> W;
// vector<vector<int>> matrix(H,vector<int>(W,0));
//
// for(int i = 0;i < H;i++){
// for(int j = 0; j < W;j++){
// char tmp;
// cin >> tmp;
// if(tmp == 'F'){
// matrix[i][j] = 1;
// }else if(tmp == 'R'){
// matrix[i][j] = 2;
// }
// }
// }
// vector<vector<int>> min_dist(H,vector<int>(W,INT_MAX));
// int ans = 0;
// min_dist[0][0] = 1;
// dfs(0,0,matrix,min_dist);
// for(int i = 0; i < H;i++){
// for(int j = 0; j < W;j++){
// if(matrix[i][j] != 0){
// ans = max(min_dist[i][j],ans);
// // cout << min_dist[i][j] << " ";
// }
// // else{
// // cout << 0 << " ";
// // }
// }
// // cout << endl;
// }
// cout << ans;
// }
#include <bits/stdc++.h>
using namespace std;
int H, W;
int dx[4] = {0, 1, -1, 0};
int dy[4] = {1, 0, 0, -1};
int bfs_min_animals(vector<vector<int>>& matrix) {
vector<vector<int>> min_dist(H, vector<int>(W, INT_MAX));
deque<pair<int, int>> q;
// Start from the top-left corner
q.push_front({0, 0});
min_dist[0][0] = 1; // First animal starts at (0,0)
while (!q.empty()) {
int r = q.front().first;
int c = q.front().second;
q.pop_front();
for (int i = 0; i < 4; ++i) {
int newX = r + dx[i];
int newY = c + dy[i];
if (newX < 0 || newY < 0 || newX >= H || newY >= W) continue;
if (matrix[newX][newY] == 0) continue; // Untouched snow
// Calculate the new cost
int newDist = min_dist[r][c];
if (matrix[newX][newY] != matrix[r][c]) {
newDist++; // Different track, increase animal count
}
if (newDist < min_dist[newX][newY]) {
min_dist[newX][newY] = newDist;
if (matrix[newX][newY] == matrix[r][c]) {
q.push_front({newX, newY}); // Same track, prioritize by pushing to front
} else {
q.push_back({newX, newY}); // Different track, explore later
}
}
}
}
// The answer is the maximum value in the min_dist matrix
int ans = 0;
for (int i = 0; i < H; ++i) {
for (int j = 0; j < W; ++j) {
if (matrix[i][j] != 0) {
ans = max(ans, min_dist[i][j]);
}
}
}
return ans;
}
int main() {
cin.tie(0);
ios_base::sync_with_stdio(0);
cin >> H >> W;
vector<vector<int>> matrix(H, vector<int>(W, 0));
for (int i = 0; i < H; i++) {
for (int j = 0; j < W; j++) {
char tmp;
cin >> tmp;
if (tmp == 'F') {
matrix[i][j] = 1;
} else if (tmp == 'R') {
matrix[i][j] = 2;
}
}
}
cout << bfs_min_animals(matrix) << "\n";
return 0;
}
