Problem:
Score : 300 points

Problem Statement

Dolphin resides in two-dimensional Cartesian plane, with the positive x-axis pointing right and the positive y-axis pointing up.

Currently, he is located at the point (sx,sy). In each second, he can move up, down, left or right by a distance of 1.

Here, both the x- and y-coordinates before and after each movement must be integers.

He will first visit the point (tx,ty) where sx < tx and sy < ty, then go back to the point (sx,sy), then visit the point (tx,ty) again, and lastly go back to the point (sx,sy).

Here, during the whole travel, he is not allowed to pass through the same point more than once, except the points (sx,sy) and (tx,ty).

Under this condition, find a shortest path for him.

Constraints

-1000 ≤ sx < tx ≤ 1000

-1000 ≤ sy < ty ≤ 1000

sx,sy,tx and ty are integers.

Input

The input is given from Standard Input in the following format:

sx sy tx ty

Output

Print a string S that represents a shortest path for Dolphin.

The i-th character in S should correspond to his i-th movement.

The directions of the movements should be indicated by the following characters:

U: Up

D: Down

L: Left

R: Right

If there exist multiple shortest paths under the condition, print any of them.

Sample Input 1

0 0 1 2

Sample Output 1

UURDDLLUUURRDRDDDLLU

One possible shortest path is:

Going from (sx,sy) to (tx,ty) for the first time: (0,0) → (0,1) → (0,2) → (1,2)

Going from (tx,ty) to (sx,sy) for the first time: (1,2) → (1,1) → (1,0) → (0,0)

Going from (sx,sy) to (tx,ty) for the second time: (0,0) → (-1,0) → (-1,1) → (-1,2) → (-1,3) → (0,3) → (1,3) → (1,2)

Going from (tx,ty) to (sx,sy) for the second time: (1,2) → (2,2) → (2,1) → (2,0) → (2,-1) → (1,-1) → (0,-1) → (0,0)

Sample Input 2

-2 -2 1 1

Sample Output 2

UURRURRDDDLLDLLULUUURRURRDDDLLDL

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

#pragma warning disable

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using System.Text;
using System.Text.RegularExpressions;
using System.Diagnostics;
using System.Numerics;
using System.Collections;
using System.Timers;

static class MainClass
{
    public static void Main(string[] args)
    {
        var sstt = Console.ReadLine().SplittedStringToInt32List();
        var sx = sstt[0];
        var sy = sstt[1];
        var tx = sstt[2];
        var ty = sstt[3];

        var nowx = sx;
        var nowy = sy;
        var sb = new StringBuilder();
        var value = new StringBuilder();
        string dele, uele, lele, rele;

        while (true)
        {
            if (nowx == tx)
                break;
            nowx++;
            sb.Append("R");
        }
        rele = sb.ToString();
        value.Append(sb.ToString());
        sb.Clear();
        while (true)
        {
            if (nowy == ty)
                break;
            nowy++;
            sb.Append("U");
            
        }
        uele = sb.ToString();
        value.Append(sb.ToString());
        sb.Clear();
        while (true)
        {
            if (nowx == sx)
                break;
            sb.Append("L");
            nowx--;
        }
        lele = sb.ToString();
        value.Append(sb.ToString());
        sb.Clear();
        while (true)
        {
            if (nowy == sy)
                break;
            nowy--;
            sb.Append("D");
        }
        dele = sb.ToString();
        value.Append(sb.ToString());
        sb.Clear();
        value.Append("D").Append(rele).Append("R").Append("U").Append(uele).Append("L").Append("U").Append("L").Append(lele).Append("D").Append(dele).Append("R");
        Console.WriteLine(value.ToString());
        Console.ReadLine();
    }


    //public class Edge
    //{
    //    public int From;
    //    public int To;
    //    public int Cost;
    //}

    //public static List<KeyValuePair<int, int>> GetShortestPathes(int s, IEnumerable<Edge> edges, int vertices)
    //{
    //    var ls = new KeyValuePair<int, int>[vertices];

    //    return ls.ToList();
    //}


    #region ライブラリ

    #region 文字列処理

    public static int ToInt32(this string str) => int.Parse(str);
    public static BigInteger ToBigInteger(this string str) => BigInteger.Parse(str);
    public static List<string> SplittedStringToList(this string str) => str.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToList();
    public static List<int> SplittedStringToInt32List(this string str) => str.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).Select(x => int.Parse(x)).ToList();

    public static List<BigInteger> SplittedStringToBigInteger(this string str) => str.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).Select(x => BigInteger.Parse(x)).ToList();
    #endregion
    #region DeepClone
    public static T DeepClone<T>(this T src)
    {
        using (var memoryStream = new MemoryStream())
        {
            var binaryFormatter
              = new BinaryFormatter();
            binaryFormatter.Serialize(memoryStream, src);
            memoryStream.Seek(0, SeekOrigin.Begin);
            return (T)binaryFormatter.Deserialize(memoryStream);
        }
    }
    #endregion

    public static int Gcd(int a, int b)
    {
        if (b == 0)
            return a;
        return Gcd(b, a % b);
    }
    public static BigInteger Gcd(BigInteger a, BigInteger b)
    {
        if (b == 0)
            return a;
        return Gcd(b, a % b);
    }


    public static BigInteger Factorial(int n)
    {
        var dp = new BigInteger[n];
        dp[0] = 1;
        for (int i = 1; i < n; i++)
        {
            dp[i] = dp[i - 1] * (i + 1);
        }
        return dp[n - 1];
    }

    public static List<int> PrimeFactorize(int n)
    {
        var bases = n;
        var num = (int)Math.Pow(n, 0.5);
        var ls = new List<int>();
        for (int i = 2; i <= num; i++)
        {
            if (n % i == 0)
            {
                n = n / i;
                ls.Add(i);
                i--;
                continue;
            }
        }
        var nnn = 1;
        foreach (var item in ls)
        {
            nnn = nnn * item;
        }
        if (nnn != bases)
            ls.Add(n);
        return ls;
    }

    #endregion

}