Problem:
Score : 100 points

Problem Statement

There are N children in AtCoder Kindergarten. Mr. Evi will arrange the children in a line, then give 1 candy to the first child in the line, 2 candies to the second child, ..., N candies to the N-th child. How many candies will be necessary in total?

Constraints

1≦N≦100

Input

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

N

Output

Print the necessary number of candies in total.

Sample Input 1

3

Sample Output 1

6

The answer is 1+2+3=6.

Sample Input 2

10

Sample Output 2

55

The sum of the integers from 1 to 10 is 55.

Sample Input 3

1

Sample Output 3

1

Only one child. The answer is 1 in this case.

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

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

namespace AtCoder
{
    public class IO
    {
        public static string ReadStr() => Console.ReadLine();
        public static string[] ReadStrArr() => ReadStr().Split(' ');

        public static int ReadInt() => int.Parse(ReadStr());
        public static int[] ReadIntArr() => Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse);

        public static double ReadDouble() => double.Parse(ReadStr());
        public static double[] ReadDoubleArr() => Array.ConvertAll(Console.ReadLine().Split(' '), double.Parse);

        public static long ReadLong() => long.Parse(ReadStr());
        public static long[] ReadLongArr() => Array.ConvertAll(Console.ReadLine().Split(' '), long.Parse);
    }

    class Template
    {
        static void Main(string[] args)
        {
            int n = IO.ReadInt();
            Console.WriteLine((1 + n) * n / 2);
        }
    }
}