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;
using System.Collections;
using System.Collections.Generic;
using static System.Console;
class Program
{
    static void Main()
    {
        //入力
        //int[] input = Console.ReadLine().Split().Select(i => int.Parse(i)).ToArray();
        //string input= Console.ReadLine();
        int input =int.Parse(Console.ReadLine());
        Console.WriteLine(input*(input+1)/2);


        /*
        //処理速度計測
        var sw = new System.Diagnostics.Stopwatch();
        sw.Start();
        //解法
 
        //処理速度表示
        sw.Stop();
        TimeSpan ts = sw.Elapsed;
        Console.WriteLine((int)(Math.Floor((ts).TotalMilliseconds))+"ms");
        */
        Console.ReadLine();

    }
}