#include <bits/stdc++.h>
using namespace std;
int n, m;
int dx[4] = {-1, 1, 0, 0}, dy[4] = {0, 0, -1, 1};
bool check(int nx, int ny){
return (nx >= 0 && nx < n && ny >= 0 && ny < m);
}
struct item{
int x, y, dist;
};
struct comp{
bool operator()(item a, item b){
return (a.dist < b.dist) || (a.dist == b.dist && make_pair(a.x, a.y) < make_pair(b.x, b.y));
}
};
int bfs(vector<vector<char>>& grid){
priority_queue<item, vector<item>, comp> q;
q.push({0, 0, 1});
vector<vector<int>> dist(n, vector<int>(m, 1e9));
dist[0][0] = 1;
while (!q.empty()){
item i = q.top(); q.pop();
if (dist[i.x][i.y] != i.dist) continue;
for (int j = 0; j < 4; j++){
int nx = i.x + dx[j], ny = i.y + dy[j];
if (!check(nx, ny)) continue;
if (grid[nx][ny] == '.') continue;
int ndist = i.dist + (grid[nx][ny] != grid[i.x][i.y]);
if (ndist < dist[nx][ny]){
dist[nx][ny] = ndist;
q.push({nx, ny, ndist});
}
}
}
//max distance
int mx = 0;
for (int i = 0; i < n; i++){
for (int j = 0; j < m; j++){
//cout << (dist[i][j] == 1e9 ? 0 : dist[i][j]) << ' ';
if (grid[i][j] == '.') continue;
if (dist[i][j] > mx){
mx = dist[i][j];
}
}
//cout << '\n';
}
return mx;
}
int main(){
cin.tie(0)->sync_with_stdio(0);
cin >> n >> m;
vector<vector<char>> grid(n, vector<char>(m));
vector<int> cnt(2, 0); //r, f
for (int i = 0; i < n; i++){
for (int j = 0; j < m; j++){
cin >> grid[i][j];
if (grid[i][j] == 'F') cnt[1]++;
if (grid[i][j] == 'R') cnt[0]++;
}
}
//empty
if (grid[0][0] == '.'){
cout << "0\n";
return 0;
}
//ans
cout << bfs(grid) << '\n';
}
