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

public class Main {

    private static Scanner in;

    static BigInteger [][]dp=new BigInteger [100005][3];
    public static void main(String[] args) {
        in = new Scanner(System.in); 
        dp[1][1]=BigInteger.valueOf(1);
        dp[1][2]=BigInteger.valueOf(0);
        for(int i=2;i<=205;i++){
            dp[i][1]=dp[i-1][1].add(dp[i-1][2]);
            dp[i][2]=dp[i-1][1];
        }
        while(in.hasNext()){
            int n=in.nextInt();
            System.out.println(dp[n][1].add(dp[n][2]));
        }
    }
}