#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <cmath>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdio.h>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <unordered_map>
using namespace std;
#define int long long
#define MOD 1000000007
#define INF 2000000000
#define IN 100001
#define LOG 17
#define MINF -2000000000
#define all(x) x.begin(),x.end()
#define ios ios_base::sync_with_stdio(0);cin.tie(0);
void solution(){
int n,m; cin >> n >> m;
vector<string> arr(n);
for(int i = 0; i < n; i++){
cin >> arr[i];
}
int ans = -1;
bool ok = false;
bool ch = false;
for(int i = 0; i < n; i++){
int cnt = 0;
for(int j = 0; j < m; j++){
if(arr[i][j] == 'R') ok = true;
if(arr[i][j] == 'F') ch = true;
if(j == 0){
if(arr[i][j] != '.') cnt++;
}else{
if(arr[i][j] != arr[i][j-1] && arr[i][j-1] == '.') cnt++;
}
}
ans = max(ans , cnt);
}
// cout << ok << " " << ch << endl;
if(ok == true && ch == true) cout << ans+1 << endl;
else cout << ans << endl;
}
signed main(){
ios
int t = 1;
// cin >> t;
while(t--){
solution();
}
return 0;
}
