import java.util.*;
public class Main {
	public static void main(String[] args){
		// 文字列の入力
		Scanner sc = new Scanner(System.in);
        String someString = sc.next();
		char rChar = 'R';
        int rCount = 0;
      
		for (int i = 0; i < someString.length(); i++) {
        if(rCount==0 && someString.charAt(i) == rChar){
          rCount = 1;
        }
        if (someString.charAt(i) == rChar) {
          if(i>0 && someString.charAt(i-1) == rChar){
           rCount++;
          }
        }         
        }
      
      System.out.println(rCount);
      
	}
}
/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