#include<bits/stdc++.h>
using namespace std;
int main(){
  string s;
  cin >> s;
  int ans = 0;
  int o = 0;
  for(int i = 0;i<3;i++){
    if(s[i]=='R') o++;
    else o = 0;
    ans = max(o,ans);
  }
  cout << ans;
}