import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
System.out.println(fibonacci(n));
}
private static int fibonacci(int n) {
if(n == 0) return 0;
if(n == 1) return 1;
return fibonacci(n-1) + fibonacci(n-2);
}
}