Problem:
Score : 100 points

Problem Statement

Given are two strings S and T consisting of lowercase English letters. Concatenate T and S in this order, without space in between, and print the resulting string.

Constraints

S and T are strings consisting of lowercase English letters.

The lengths of S and T are between 1 and 100 (inclusive).

Input

Input is given from Standard Input in the following format:

S T

Output

Print the resulting string.

Sample Input 1

oder atc

Sample Output 1

atcoder

When S = oder and T = atc, concatenating T and S in this order results in atcoder.

Sample Input 2

humu humu

Sample Output 2

humuhumu

Solution in C# (.NET Core 3.1.201) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AtCoder2 {
	class Program {
		static void Main(string[] args) {

			var inputArray = retreiveStringArray();
			var inputCount = 2;

			// 不正な入力は処理しない
			if (inputArray.Length != inputCount) {
				Console.WriteLine("invalid input");
				return;
			}
			var N = inputArray[0];
			var K = inputArray[1];

	


			//答えの出力
			var ans = N + K;
			Console.WriteLine(ans);

		}

		/// <summary>
		/// 同じ手を出せないことによって生じる損失点数
		/// </summary>
		/// <param name="K"></param>
		/// <param name="point"></param>
		/// <param name="jankenList"></param>
		/// <returns></returns>
		private static long calLossPoint(long K, long point, HashSet<long> jankenList) {

			var changeList = new HashSet<long>();//K番先に同じ手がある場合、書き換える。書き換えた番号を覚えておくリスト
			var count = 0;
			foreach (var r in jankenList) {

				if (changeList.Contains(r)) {
					continue;
				}

				if (jankenList.Contains(r + K)) {
					count++;
					changeList.Add(r + K);
				}
			}
			return point * count;
		}

		/// <summary>
		/// スペースで区切られた文字列配列の入力を受け取る
		/// </summary>
		/// <returns></returns>
		private static string[] retreiveStringArray() {
			var inputArray = Console.ReadLine().Split(' ');
			return inputArray;
		}

		/// <summary>
		/// スペースで区切られた整数配列の入力を受け取る
		/// </summary>
		/// <returns></returns>
		private static long[] retreiveLongArray() {
			var inputArray = Console.ReadLine().Split(' ');
			var longArray = inputArray.Select(s => long.Parse(s));
			return longArray.ToArray();
		}
	}
}