import java.util.*;
import java.math.*;

public class Main {
    
    public static BigDecimal[][] dp = new BigDecimal[300][2];
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        
        Scanner in = new Scanner(System.in);
        
        dp[1][0] = new BigDecimal("1");
        dp[1][1] = new BigDecimal("0");
        
        for(int i = 2 ; i <= 210; i++)
        {
            
            dp[i][0] = dp[i-1][0].add(dp[i-1][1]);
            dp[i][1] = dp[i-1][0];
        }
        
        while(in.hasNext())
        {
            int n = in.nextInt();
            if(n < 1 || n > 200)
                System.out.println();
            else
                System.out.println(dp[n][0].add(dp[n][1]));
        }
        
    }

}