#include <bits/stdc++.h>
using namespace std;
using ll = long long int;
vector<ll> xcord = {0,0,1,-1};
vector <ll> ycord = {1, -1, 0, 0};
struct cord{
ll x,y;
};
void solve() {
ll n,m;
cin >> n >> m;
vector <vector <char>> l1(n);
vector <vector <bool>> visited(n+1, vector<bool>(m, false));
for (int i = 0; i < n; i++){
string s;
cin >> s;
for (auto &p : s){
l1[i].push_back(p);
}
}
queue <cord> rabbits;
queue <cord> foxes;
auto selection = [&](ll x, ll y){
if (visited[x][y]){
return;
}
visited[x][y] = true;
if (l1[x][y] == 'F'){
foxes.push({x,y});
}
else if (l1[x][y] == 'R'){
rabbits.push({x,y});
}
};
auto flag = [&](ll x, ll y){
if (x >= 0 && x < n && y >= 0 && y < m && (l1[x][y] == 'R' || l1[x][y] == 'F')){
return true;
}
return false;
};
selection(0LL,0LL);
ll answ = 0;
while (rabbits.size() >= 1 || foxes.size() >= 1){
if(rabbits.size() >= 1){
answ += 1;
}
while (rabbits.size() >= 1){
auto cur = rabbits.front();
rabbits.pop();
visited[cur.x][cur.y] = true;
for (int i = 0; i < 4; i++){
if (flag(cur.x + xcord[i], cur.y + ycord[i])){
selection(cur.x + xcord[i], cur.y + ycord[i]);
}
}
}
if(foxes.size() >= 1){
answ += 1;
}
while (foxes.size() >= 1){
auto cur = foxes.front();
foxes.pop();
visited[cur.x][cur.y] = true;
for (int i = 0; i < 4; i++){
if (flag(cur.x + xcord[i], cur.y + ycord[i])){
selection(cur.x + xcord[i], cur.y + ycord[i]);
}
}
}
}
cout << answ << "\n";
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
solve();
return 0;
}
