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