using System;
namespace t1068{
    class Program{
        public static void Main(string[] args){
            int n = int.Parse(Console.ReadLine());
            int i = 0;
            while (n != 1){
                if (n >= 1){
                    i+= n;
                    n--;
                }
                else if (n <= 0){
                    i+= n;
                    n++;
                }
            }
            Console.Write(i + 1);
            //Console.ReadKey();
        }
    }
}

    using System;

    class Puzzle
    {
        public static void Main()
        {
            var n = int.Parse(Console.In.ReadLine());
            (int start, int end) = n > 1 ? (1, n) : (n, 1);

            int sum = 0;

            for (int i = start; i <= end; i++)
                sum += i;

            Console.WriteLine(sum);
        }
    }

 static int Proccess(int input)
    {
        if (input == 1)
        {
            return 2;
        }
        else if (input == 0)
        {
            return 1;
        }

        bool isInputNegative = false;
        if (input < 0)
        {
            input = input * -1;
            isInputNegative = true;
        }
        int sum = 0;
        for (int i = 1; i < input + 1; i++)
        {
            sum += i;
        }

        if (isInputNegative)
        {
            sum = sum * -1;
            sum++;
        }
        return sum;
    }


more understandable :D

Edited by author 11.11.2017 20:22