[BaekJoon] #10870 피보나치

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        Scanner in = new Scanner(System.in);

        int N = in.nextInt();

        int sum = fib(N);
        System.out.println(sum);
    }

    public static int fib (int N) {
        if(N == 0) return 0;
        if(N == 1) return 1;
        return fib(N - 1) + fib(N - 2);
    }

}