import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s3 = sc.next();
        String[] split = s3.split("");
        int rain=0;
        int a=0;
        for(int i=0; i<3; i++) {
            if(split[i].equals("R")) {
                rain += 1;
            }else if(split[i].equals("S")){
                if(rain == 2||rain == 1) {
                    break;
                }else {
                    rain = 0;
                }
            }
        }
        System.out.println(rain);
    }
}
/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