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

public class Main {

    public static void main(String[] args) {
        BigInteger[][] Big = new BigInteger[222][2];
        String num1 = "1";
        String num0 = "0";
        Big[1][0] = new BigInteger(num1);
        Big[1][1] = new BigInteger(num0);
        Big[2][0] = new BigInteger(num1);
        Big[2][1] = new BigInteger(num1);
        for(int  i = 3; i <= 200; i++){
            Big[i][1] = Big[i-1][0];
            Big[i][0] = Big[i-1][0].add(Big[i-1][1]);
       //     System.out.println(Big[i][1]);
        //    System.out.println(Big[i][0]);
        }
        Scanner input = new Scanner(System.in);
        while(input.hasNext()){
            int n = input.nextInt();
    //        System.out.println(Big[n][0]);
     //       System.out.println(Big[n][1]);
            System.out.println(Big[n][0].add(Big[n][1]));
        }
        input.close();
   //     System.out.println("加法操作:" + big1.add(big2));
   //     System.out.println("减法操作:" + big1.subtract(big2));
    //    System.out.println("乘法操作:" + big1.multiply(big2));
   //     BigInteger result[] = big1.divideAndRemainder(big2);
    //    System.out.println("相除后的商是:" + result[0]);
   //     System.out.println("相除后的余数是:" + result[1]);
    }
}