Dp1

using System;
using System.Reflection.Emit;

namespace ConsoleApplication1945
{
    internal class Program
    {
        public static void Main()
        {
            Console.WriteLine(Fib(10));
        }

        public static int Fib(int number)
        {
            if (number < 0) throw new ArgumentException();

            var first = 0;
            var second = 1;

            if (number == 0) return first;
            if (number == 1) return second;

            for (var i = 2; i <= number; i++)
            {
                var temp = first + second;
                first = second;
                second = temp;
            }

            return second;
        }
    }
}