import java.util.Scanner;
import java.math.*;
public class Main
{
    public static void main(String args[])
    {
        Scanner in=new Scanner(System.in);
        int n;
        BigInteger[] a=new BigInteger[1000];
        a[1]=BigInteger.valueOf(1);
        a[2]=BigInteger.valueOf(2);
        for(int i=3;i<=500;i++)
        {
            a[i]=a[i-1].add(a[i-2]);
        }
        while(in.hasNext()){
            n=in.nextInt();
            System.out.println(a[n]);
        }
        
    }

}