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


class Fibonacci
{
    static void Main()
    {
        int[] x = new int[5000];

        int y;
        int i = 2;
        int sum = 0;
        System.Console.WriteLine("請輸入第N個Fibonacci數 N = 0~5000之間");
        y = Convert.ToInt32(Console.ReadLine());

        for (; i < y; i++)
        {
            x[0] = 0;
            x[1] = 1;
            x[i] = x[i - 1]+ x[i - 2];
            sum = x[i];
        }
        System.Console.WriteLine("第{0}個數是:{1}", y,sum);

    }
}