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

public class Main {//fibs[20] = 6765 ,fibs的上限达到上千位

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        BigInteger[] fibs = new BigInteger[2000];

        fibs[1] = new BigInteger("1");
        fibs[2] = new BigInteger("1");

        int i;
        for(i = 3 ; i < 2000 ; ++i){
            fibs[i] = fibs[i-1].add(fibs[i-2]);
        }

        while(scanner.hasNext()){
            int n = scanner.nextInt();

            System.out.println(fibs[n+1]);
        }
    }

}