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.Linq;

namespace TestTemplate
{
    class Program
    {
        static void Main()
        {
            var a = ReadInt();
            var sum = 1;
            for (int i = 0; i < a-1; i++)
            {
                sum += i + 2;
            }
            Console.WriteLine(sum.ToString());
        }

        public static string ReadLine() => Console.ReadLine();
        public static int ReadInt() => int.Parse(ReadLine());
        public static int[] ReadIntArray() => ReadLine().Split(' ').Select(v => int.Parse(v)).ToArray();
        public static string[] ReadStrArray() => ReadLine().Split(' ').ToArray();
    }
}