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 ABC043A
{
    class Program
    {
        static void Main(string[] args)
        {
            int n;   //人数
            int s;//必要な枚数
            int i;
            //人数を入力
            n = int.Parse(Console.ReadLine());
            //必要な枚数を求める
            //（合計を求めるメルアルゴリズム）
            s = 0;    //合計を0に初期化
             for (i=1; i<=n;  i++)　//i→0の繰り返し
            {
                s = s + i;　// sを1増やす
            }

             //出力
            Console.WriteLine(s);
        }
    }
}