#include <bits/stdc++.h>
using namespace std;
int main()
{
// freopen("input.in", "r", stdin);
int height, width; cin >> height >> width;
vector<string> grid(height);
for(int i=0; i<height; i++) cin >> grid[i];
int tot = 0;
char curanimal = grid[0][0];
vector<vector<bool>> vis(height, vector<bool>(width, false)); vis[0][0] = true;
queue<pair<int, int>> foxq;
queue<pair<int, int>> rabbitq;
if(curanimal == 'F') foxq.push({0,0});
else rabbitq.push({0,0});
while(!foxq.empty() || !rabbitq.empty()){
tot++;
if(foxq.empty()){
while(!rabbitq.empty()){
//working with rabbits
//flood fill
auto cur = rabbitq.front(); rabbitq.pop();
if(cur.first > 0 && !vis[cur.first-1][cur.second]){
//flood up
if(grid[cur.first-1][cur.second] == 'F') foxq.push({cur.first-1, cur.second});
else if(grid[cur.first-1][cur.second] == 'R') rabbitq.push({cur.first-1, cur.second});
vis[cur.first-1][cur.second] = true;
}
if(cur.first < height-1 && !vis[cur.first+1][cur.second]){
//flood down
if(grid[cur.first+1][cur.second] == 'F') foxq.push({cur.first+1, cur.second});
else if(grid[cur.first+1][cur.second] == 'R') rabbitq.push({cur.first+1, cur.second});
vis[cur.first+1][cur.second] = true;
}
if(cur.second > 0 && !vis[cur.first][cur.second-1]){
//flood left
if(grid[cur.first][cur.second-1] == 'F') foxq.push({cur.first, cur.second-1});
else if(grid[cur.first][cur.second-1] == 'R') rabbitq.push({cur.first, cur.second-1});
vis[cur.first][cur.second-1] = true;
}
if(cur.second < width-1 && !vis[cur.first][cur.second+1]){
//flood right
if(grid[cur.first][cur.second+1] == 'F') foxq.push({cur.first, cur.second+1});
else if(grid[cur.first][cur.second+1] == 'R') rabbitq.push({cur.first, cur.second+1});
vis[cur.first][cur.second+1] = true;
}
}
}
else{
while(!foxq.empty()){
//working with foxes
auto cur = foxq.front(); foxq.pop();
if(cur.first > 0 && !vis[cur.first-1][cur.second]){
//flood up
if(grid[cur.first-1][cur.second] == 'F') foxq.push({cur.first-1, cur.second});
else if(grid[cur.first-1][cur.second] == 'R') rabbitq.push({cur.first-1, cur.second});
vis[cur.first-1][cur.second] = true;
}
if(cur.first < height-1 && !vis[cur.first+1][cur.second]){
//flood down
if(grid[cur.first+1][cur.second] == 'F') foxq.push({cur.first+1, cur.second});
else if(grid[cur.first+1][cur.second] == 'R') rabbitq.push({cur.first+1, cur.second});
vis[cur.first+1][cur.second] = true;
}
if(cur.second > 0 && !vis[cur.first][cur.second-1]){
//flood left
if(grid[cur.first][cur.second-1] == 'F') foxq.push({cur.first, cur.second-1});
else if(grid[cur.first][cur.second-1] == 'R') rabbitq.push({cur.first, cur.second-1});
vis[cur.first][cur.second-1] = true;
}
if(cur.second < width-1 && !vis[cur.first][cur.second+1]){
//flood right
if(grid[cur.first][cur.second+1] == 'F') foxq.push({cur.first, cur.second+1});
else if(grid[cur.first][cur.second+1] == 'R') rabbitq.push({cur.first, cur.second+1});
vis[cur.first][cur.second+1] = true;
}
}
}
}
cout << tot << endl;
}
