#include <bits/stdc++.h>
typedef long long ll;
typedef long double ld;
using namespace std;
vector<pair<int,int>> dirs = {{0,-1},{0,1},{-1,0},{1,0}};
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int R, C; cin >> R >> C;
vector<string> v(R);
for(auto &x: v) cin >> x;
vector<vector<bool>> visited(R,vector<bool>(C,false));
int cnts = 0;
queue<pair<int,int>> rabbits;
queue<pair<int,int>> foxes;
if(v[0][0] == 'R') {
rabbits.push({0,0});
} else if(v[0][0] == 'F') {
foxes.push({0,0});
}
while(true) {
// cout << "rabbits: " << rabbits.size() << " foxes: " << foxes.size() << "\n";
if(rabbits.size()) {
while(rabbits.size()) {
pair<int,int> p = rabbits.front();
rabbits.pop();
if(visited[p.first][p.second]) {
continue;
}
// cout << "rabbit bfs: " << p.first << " " << p.second << "\n";
visited[p.first][p.second] = true;
for(auto x : dirs) {
int r = p.first + x.first;
int c = p.second + x.second;
if(r >= 0 && r < R && c >= 0 && c < C) {
if(v[r][c] == 'F' && !visited[r][c]) {
foxes.push({r,c});
} else if(v[r][c] == 'R' && !visited[r][c]) {
rabbits.push({r,c});
}
}
}
}
} else if(foxes.size()) {
while(foxes.size()) {
pair<int,int> p = foxes.front();
foxes.pop();
if(visited[p.first][p.second]) {
continue;
}
// cout << "fox bfs: " << p.first << " " << p.second << "\n";
visited[p.first][p.second] = true;
for(auto x : dirs) {
int r = p.first + x.first;
int c = p.second + x.second;
if(r >= 0 && r < R && c >= 0 && c < C) {
if(v[r][c] == 'F' && !visited[r][c]) {
foxes.push({r,c});
} else if(v[r][c] == 'R' && !visited[r][c]) {
rabbits.push({r,c});
}
}
}
}
} else {
break;
}
cnts++;
}
cout << cnts << "\n";
return 0;
}
