import java.util.Scanner;
public class Main {
// 计算小乐乐可以走的方法数
public static int show(int n) {
if(n == 1) {
return 1;
} else if(n == 2) {
return 2;
} else {
return show(n-1)+show(n-2);
}
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int result = show(n);
System.out.println(show(n));
}
}