Problem:
﻿Score: 100 points

Problem Statement

In 2020, AtCoder Inc. with an annual sales of more than one billion yen (the currency of Japan) has started a business in programming education.

One day, there was an exam where a one-year-old child must write a program that prints Hello World, and a two-year-old child must write a program that receives integers A, B and prints A+B.

Takahashi, who is taking this exam, suddenly forgets his age.

He decides to write a program that first receives his age N (1 or 2) as input, then prints Hello World if N=1, and additionally receives integers A, B and prints A+B if N=2.

Write this program for him.

Constraints

N is 1 or 2.

A is an integer between 1 and 9 (inclusive).

B is an integer between 1 and 9 (inclusive).

Input

Input is given from Standard Input in one of the following formats:

1

2
A
B

Output

If N=1, print Hello World; if N=2, print A+B.

Sample Input 1

1

Sample Output 1

Hello World

As N=1, Takahashi is one year old. Thus, we should print Hello World.

Sample Input 2

2
3
5

Sample Output 2

8

As N=2, Takahashi is two years old. Thus, we should print A+B, which is 8 since A=3 and B=5.

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

using System;

namespace AtCoder.Common {
    class Dxxx {
        static void Main() => Solve();

        static void Solve() {
            var a = ReadInt();
            if (a == 1) {
                WriteAnswer("Hello World");
            } else {
                WriteAnswer(ReadInt() + ReadInt());
            }
        }

        static string ReadString() => Console.ReadLine().Trim();
        static int ReadInt() => int.Parse(ReadString());
        static long ReadLong() => long.Parse(ReadString());
        static float ReadFloat() => float.Parse(ReadString());
        static double ReadDouble => double.Parse(ReadString());

        static string[] ReadStringArray() => ReadString().Split(' ');
        static int[] ReadIntArray() => Array.ConvertAll(ReadString().Split(' '), int.Parse);
        static long[] ReadLongArray() => Array.ConvertAll(ReadString().Split(' '), long.Parse);
        static float[] ReadFloatArray() => Array.ConvertAll(ReadString().Split(' '), float.Parse);
        static double[] ReadDoubleArray() => Array.ConvertAll(ReadString().Split(' '), double.Parse);

        static T TypeConversion<T>(string s) {
            if (typeof(T) == typeof(int)) {
                return (T) Convert.ChangeType(int.Parse(s), typeof(T));
            } else if (typeof(T) == typeof(long)) {
                return (T) Convert.ChangeType(long.Parse(s), typeof(T));
            } else if (typeof(T) == typeof(double)) {
                return (T) Convert.ChangeType(double.Parse(s), typeof(T));
            } else {
                return (T) Convert.ChangeType(s, typeof(T));
            }
        }

        static void ReadMulti<T, U>(out T a, out U b) {
            var str = ReadStringArray();
            a = TypeConversion<T>(str[0]);
            b = TypeConversion<U>(str[1]);
        }

        static void ReadMulti<T, U, V>(out T a, out U b, out V c) {
            var str = ReadStringArray();
            a = TypeConversion<T>(str[0]);
            b = TypeConversion<U>(str[1]);
            c = TypeConversion<V>(str[2]);
        }

        static void WriteAnswer(object ans) => Console.WriteLine(ans);
    }
}