package PredvaritelnoAdvanced.StacksAndQueues.classTwo;

import java.util.ArrayDeque;
import java.util.Scanner;

public class G_RecursiveFibonacci_07 {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int num = Integer.parseInt(scanner.nextLine());
        ArrayDeque<Long> stack = new ArrayDeque<>();
        for (int i = 0; i < num + 1; i++) {
            if (i <= 1) {
                stack.push(1L);
            } else {
                long numOne = stack.pop();
                long numTwo = stack.pop();
                long numThree = numOne + numTwo;
                stack.push(numTwo);
                stack.push(numOne);
                stack.push(numThree);
            }
        }
        System.out.println(stack.peekFirst());
    }
}