import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		String S = scan.next();
		String[] Sarray = S.split("");

//		for (int i = 0; i < 3; i++) {
//			Sarray[i] = S.charAt(i);
//		}


		int count = 0;
		if(!(Sarray[0].equals("R")) && !(Sarray[1].equals("R")) && !(Sarray[2].equals("R"))){
			count = 0;
			System.out.println(count);
			return;
		}
		if(Sarray[0].equals("R") && Sarray[1].equals("R") && Sarray[2].equals("R")){
			count = 3;
			System.out.println(count);
			return;
		}
		if(Sarray[0].equals("R") && Sarray[1].equals("R")){
			count = 2;
			System.out.println(count);
			return;
		}
		if(Sarray[1].equals("R") && Sarray[2].equals("R")){
			count = 2;
			System.out.println(count);
			return;
		}

		if(Sarray[0].equals("R")){
			count = 1;
			System.out.println(count);
			return;
		}
		if(Sarray[1].equals("R")){
			count = 1;
			System.out.println(count);
			return;
		}
		if(Sarray[2].equals("R")){
			count = 1;
			System.out.println(count);
			return;
		}



		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