Problem:
Score: 200 points

Problem Statement

Takahashi will do a tap dance. The dance is described by a string S where each character is L, R, U, or D. These characters indicate the positions on which Takahashi should step. He will follow these instructions one by one in order, starting with the first character.

S is said to be easily playable if and only if it satisfies both of the following conditions:

Every character in an odd position (1-st, 3-rd, 5-th, \ldots) is R, U, or D.

Every character in an even position (2-nd, 4-th, 6-th, \ldots) is L, U, or D.

Your task is to print Yes if S is easily playable, and No otherwise.

Constraints

S is a string of length between 1 and 100 (inclusive).

Each character of S is L, R, U, or D.

Input

Input is given from Standard Input in the following format:

S

Output

Print Yes if S is easily playable, and No otherwise.

Sample Input 1

RUDLUDR

Sample Output 1

Yes

Every character in an odd position (1-st, 3-rd, 5-th, 7-th) is R, U, or D.

Every character in an even position (2-nd, 4-th, 6-th) is L, U, or D.

Thus, S is easily playable.

Sample Input 2

DULL

Sample Output 2

No

The 3-rd character is not R, U, nor D, so S is not easily playable.

Sample Input 3

UUUUUUUUUUUUUUU

Sample Output 3

Yes

Sample Input 4

ULURU

Sample Output 4

No

Sample Input 5

RDULULDURURLRDULRLR

Sample Output 5

Yes

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            // 各種変数の読み込み
            var s = Console.ReadLine().ToCharArray();
            bool good = true;
            for (int i = 0; i < s.Length; i++)
            {
                if (i % 2 == 1 && s[i] == 'R')
                {
                    good = false;
                    break;
                }
                else if (i % 2 == 0 && s[i] == 'L')
                {
                    good = false;
                    break;
                }
            }
            if (good)
            {
                Console.WriteLine("Yes");
            }
            else
            {
                Console.WriteLine("No");
            }
#if DEBUG
            Console.ReadKey();
#endif
        }


        private static int Readint()
        {
            // 1行に1つのintが入力されたのを読む
            return int.Parse(Console.ReadLine());
        }

        private static int[] Readints()
        {
            // 1行に複数のintが入力されたのを読む
            var s = Console.ReadLine().Split(' ');
            var output = new int[s.Length];
            for (int i = 0; i < s.Length; i++)
            {
                output[i] = int.Parse(s[i]);
            }
            return output;
        }

        private static int[][] Readints(int n, bool transpose = false)
        {
            // n行それぞれにintが入力されたのを読む
            // output[行番号][列番号]で返す。
            // transposeがtrueのときは、output[列番号][行番号]で返す。
            var s = Console.ReadLine().Split(' ');
            int rownum = s.Length;
            if (transpose)
            {
                var outputs = new int[rownum][];
                for (int j = 0; j < rownum; j++)
                {
                    outputs[j] = new int[n];
                }
                for (int i = 0; i < s.Length; i++)
                {
                    outputs[i][0] = int.Parse(s[i]);
                }
                for (int l = 1; l < n; l++)
                {
                    var temps = Console.ReadLine().Split(' ');
                    for (int i = 0; i < rownum; i++)
                    {
                        outputs[i][l] = int.Parse(temps[i]);
                    }
                }
                return outputs;
            }
            else
            {
                var outputs = new int[n][];
                outputs[0] = new int[rownum];
                for (int i = 0; i < s.Length; i++)
                {
                    outputs[0][i] = int.Parse(s[i]);
                }
                for (int l = 1; l < n; l++)
                {
                    outputs[l] = new int[rownum];
                    var temps = Console.ReadLine().Split(' ');
                    for (int i = 0; i < rownum; i++)
                    {
                        outputs[l][i] = int.Parse(temps[i]);
                    }
                }
                return outputs;
            }
        }
    }
}