import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
        char[] S = sc.next().toCharArray();
        
        int res=0;
        int count=0;
        for(int i=0; i<3; i++){
            if(S[i]=='R'){
                res++;
                count = res;
            }else{
                res = 0;
            }
        }
        
        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