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: Wrong Answer)

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

public class GFG
{
    static public void Main()
    {
        try
        {
            var n = Console.ReadLine();
            //var input1 = Console.ReadLine().Split(' ');
            //var n = int.Parse(input1[0]);
            //var L = int.Parse(input1[1]);

            //var aar = Console.ReadLine().Split(' ').Select(x => Int32.Parse(x)).ToArray();

            SubString(n);
        }
        catch (Exception ex)
        {
            Console.Write(ex);
        }
    }

    static void SubString(string s)
    {
        for (int i = 0; i < s.Length-1; i++)
        {
            if (s[i] == s[i + 1])
            {
                Console.Write((i + 1) + " " + (i + 2));
                return;
            }
            if (i + 2 < s.Length && s[i] == s[i + 2])
            {
                Console.Write((i + 1) + " " + (i + 3));
                return;
            }
        }

        Console.Write("-1 -1");

    }

    static bool UnBal(string s)
    {
        if (s.Length <= 1)
            return false;

        var ss = s.ToCharArray();
        int n = ss.Length;
        var group = ss.GroupBy(x => x).Select(g => new { l = g.Key, count = g.Count() });

        foreach (var cc in group)
        {
            if (cc.count > (n / 2))
                return true;
        }
        return false;

    }

}