using System;
using System.Linq;
class Program
{
    static void Main()
    {
        int positionInFibonacciSequence = int.Parse(Console.ReadLine());
        int[] fibonacciSequence = new int[50];

        fibonacciSequence[0] = 1;
        fibonacciSequence[1] = 1;

        if (positionInFibonacciSequence > 2)
        {
            for (int i = 2; i < positionInFibonacciSequence; i++)
            {
                fibonacciSequence[i] = fibonacciSequence[i - 1] + fibonacciSequence[i - 2];
            }
        }
        Console.WriteLine(fibonacciSequence[positionInFibonacciSequence - 1]);
    }
}