
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.math.BigDecimal;
import java.math.BigInteger;

public class Main {
	public static void main(String[] args) {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		FastInput in = new FastInput(inputStream);
		PrintWriter out = new PrintWriter(outputStream);
		ABC175A solver = new ABC175A();
		solver.solve(1, in, out);
		out.close();
	}

	static class ABC175A {

		public void solve(int testNum, FastInput in, PrintWriter out) {
			
			String s = in.next();
			
			int cnt = 0;
			int ans = 0;
			for(int i = 0 ; i < 3 ;i++) {
				if(s.charAt(i) == 'R') {
					cnt++;
					ans = Math.max(ans,cnt);
				}
				else {
					cnt = 0;
				}
			}
			
			out.println(ans);

		}

	}
static class FastInput{
	private final BufferedReader in;
	private String[] buff;
	private int index = 0;
	
	public FastInput(InputStream im) {
		in = new BufferedReader(new InputStreamReader(im));
	}
	String nextLine() {
		try {
			return in.readLine();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return null;
	}
	String next() {
		while (buff == null || index >= buff.length) {
			buff = nextLine().split(" ");
			index = 0;
		}
		return buff[index++];
	}
	int nextInt() {
		return Integer.parseInt(next());
	}
	
	long nextLong() {
		return Long.parseLong(next());
	}
	
	Double nextDouble() {
		return Double.parseDouble(next());
	}
	
	BigInteger nextBigInteger() {
		return new BigInteger(next());
	}
	
	BigDecimal nextBigDecimal() {
		return new BigDecimal(next());
	}
	
	public int[] nextIntArray(final int n) {
		final int[] res = new int [n];
		
		for(int i = 0 ; i < n ;i++) {
			res[i] = nextInt();
		}
		return res;
	}
	
	public long[] nextLongArray(final int n) {
		final long[] res= new long [n];
		
		for(int i = 0 ; i < n ;i++) {
			res[i] = nextLong();
		}
		return res;
	}
	
	public double[] nextDoubleArray(final int n ) {
		final double[] res = new double [n];
		
		for(int i = 0 ; i < n ;i++) {
			res[i] = nextDouble();
		}
		return res;
	}
	
	
	public int[][] nextInt2DArray(final int n , final int m){
		int [][]res = new int [n][m];
		
		for(int i = 0 ; i < n ;i++) {
			for(int j = 0 ; j < m ;j++) {
				res[i][j] = nextInt();
			}
		}
		return res;
	}
	public long[][] nextLong2DArray(final int n , final int m){
		long [][]res = new long [n][m];
		
		for(int i = 0 ; i < n ;i++) {
			for(int j = 0 ; j < m ;j++) {
				res[i][j] = nextLong();
			}
		}
		return res;
	}
	
	public char[][] nextChar2DArray(final int n){
		char [][]res = new char [n][];
		
		for(int i = 0 ; i < n ;i++) {
			String s = next();
			res[i] = s.toCharArray();
		}
		
		return res;
	}
}
}

/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