import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    String s = sc.nextLine();
    String r = "R";
    int count = s.indexOf(r);
    int lastcount = s.lastIndexOf(r);
    if(s.contentEquals("RRR")){
      System.out.println("3");
    }else if(s.contentEquals("SSR")){
      System.out.println("1");
    }else if(s.contentEquals("SRS")){
      System.out.println("1"); 
    }else if(s.contentEquals("RSS")){
      System.out.println("1");
    }else if(count == 0 && lastcount == 1 || count == 1 && lastcount == 2){
      System.out.println("2");
    }else if(count == 0 && lastcount == 2 || count == 2 && lastcount == -1|| count == 0 && lastcount == -1|| count == 1 && lastcount == -1 ){
      System.out.println("1");
    }else if(s.contentEquals("SSS")){
      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