#include <bits/stdc++.h>
// #pragma GCC optimize("Ofast,no-stack-protector,unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
// #define int long long
#define ll long long
#define pii pair<int, int>
#define all(v) v.begin(), v.end()
using namespace std;
const int oo = 1e9 + 9;
const int MAX = 4000 + 5, LOGMAX = 20, B = 441, MOD = 998244353;
int n, m;
bool vis[MAX][MAX][2];
vector<char> ch = {'R', 'F'};
vector<pii> dir = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
set<pii> s;
set<pii> add;
string arr[MAX];
void dfs(int x, int y, int t){
vis[x][y][t] = 1;
if(!vis[x][y][t^1]) add.insert({x, y});
for(auto d : dir){
int nx = x + d.first, ny = y + d.second;
if(nx < 1 || nx > n || ny < 1 || ny > m || vis[nx][ny][t] || arr[nx][ny] != ch[t]) continue;
dfs(nx, ny, t);
}
}
void solve(){
cin >> n >> m;
bool r = 0, f = 0;
for(int i = 1; i <= n; i++){
cin >> arr[i];
arr[i] = '%' + arr[i];
}
s.push_back({1, 1});
if(arr[1][1] == '.'){
cout << "0\n";
return;
}
int ans = -1;
int t = (arr[1][1] == 'F');
while(s.size()){
for(auto a : s){
if(vis[a.first][a.second][t]) continue;
dfs(a.first, a.second, t);
}
swap(add, s);
add.clear();
ans++;
t ^= 1;
}
cout << ans << '\n';
}
signed main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
// cin >> t;
while(t--) solve();
}
