public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int k = sc.nextInt();
int[] arr = new int[47];
arr[1] = 1;
arr[2] = 1;
for (int i = 3; i <= 46; i++) {
arr[i] = arr[i - 1] + arr[i - 2];
}
System.out.println(arr[k] + " ");