import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner s = new Scanner(System.in);

        String str = s.next();
        int count = -1;
        
        String forStr;
        for(int i=str.length(); 0<=i; i--){
            forStr = String.format(".*R{%d}.*", i);
            if(str.matches(forStr)){
                count = i;
                i=-1;
            }
        }
        System.out.println(count);
    }
}
/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