Live_Archive_6270

  import java.io.PrintWriter;
  import java.math.BigInteger;
  import java.util.Scanner;

public class Main
{
    Scanner scan=new Scanner(System.in);
    PrintWriter out=new PrintWriter(System.out);
    BigInteger dp[]=new BigInteger[10005];
    int n;
    void init(){
        dp[3]=BigInteger.valueOf(4);
        dp[4]=BigInteger.valueOf(7);
        for(int i=5;i<=10001;i++) dp[i]=dp[i-1].add(dp[i-2]);
    }

    void empezar(){
        init();
        while(scan.hasNextInt()){
             n=scan.nextInt();
             out.println(dp[n]);
             out.flush();
         }
    }
    public static void main (String[] args) throws java.lang.Exception
    {
        new Main().empezar();
    }
}