import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);		
		String s = sc.next();
        int ans = 0;
        int count = 0;
        for(int i=0;i<3;i++){if(s.charAt(i)=='R'){count++;}
                             else{ans=Math.max(ans,count);
                                 count=0;}
                            }        
		System.out.println(Math.max(ans,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