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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.*;

public class Main {
    public static void main(String[] args) {
        
        //タップダンスの動き
        String s;
        //標準入力を読み込むためのScanner
        Scanner sc = new Scanner(System.in);
        //動きやすいかどうかの結果
        String result = "yes";
        
        //タップダンスの動きを標準入力から取得
        s = sc.next();
        //文字列から"L"を探す
        for(int i = 0; i < s.length(); i++){
            //文字列に"L"が含まれている位置を取得
            int index = s.indexOf("L", i);
            
            //"L"が見つかった場合、動きづらいどうかの判定と取得位置の更新をする
                //"L"が奇数文字目にあれば動きづらい
            if(index != -1){
                if((index + 1) % 2 != 0){
                    result = "no";
                }
                //Lが見つかった位置を指定
                i = index;
            }
        }
        
        //文字列から"R"を探す
        for(int i = 0; i < s.length(); i++){
            //文字列に"R"が含まれている位置を取得
            int index = s.indexOf("R", i);
            
            //"R"が見つかった場合、動きづらいどうかの判定と取得位置の更新をする
                //"R"が偶数文字目にあれば動きづらい
            if(index != -1){    
                if((index + 1) % 2 == 0){
                    result = "no";
                }
                //Rが見つかった位置を指定
                i = index;
            }
        }
        
        //結果を出力
        System.out.println(result);

    }
}