import java.util.*;
import java.io.*;
public class Main {
  public static void main(String[] args){
   Scanner sc = new Scanner(System.in);
   String n = sc.next();
   char[] s = n.toCharArray();
   int calc = 0;
   boolean rain = false;
   for(int i=0;i<3;i++){
     if (s[i]=='R') {
       rain =true;
       if (i<2) {
       if(s[i+1]=='R'){
         calc++;
       }
      }
     }
   }
   if (rain) {
    System.out.println(calc+1);
   }
   else{
     System.out.println(0);
   }

  }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz