import java.util.*;
public class Main{
  public static void main (String args[]){
    Scanner sc = new Scanner(System.in);
    
    int ans = 0;
    String a = sc.next();
    boolean flg = true;
    
    for (int i = 0; i < 3; i++){
      String n = a.substring(i, i+1);
      if (n.equals("R") && flg){
        ans++;
      } else if (n.equals("R") && !flg){
        ans = 1;
        flg = true;
      } else {
        flg = false;
      }
    }
    
    System.out.println(ans);
  }
}
/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