import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int countRain = 0;
        String[] weather = sc.next().split("");
        boolean yesterdayIsRain = false;
        sc.close();

        for (String we : weather) {
            if ("R".equals(we)) {
                if (yesterdayIsRain) {
                    countRain++;

                } else {
                    countRain = 1;
                }
                yesterdayIsRain = true;
            } else {
                yesterdayIsRain = false;
            }
        }
        System.out.println(countRain);
    }
}
/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