import java.util.*;
import java.lang.*;
import java.io.*;

// The main method must be in a class named "Main".

public class Main {
    public static void main(String[] args) {
        int sum = fact(5);
        System.out.println(sum);
    }

    public static int fact(int n) {
        if (n <= 2) {
            return 1;
        } else {
            return fact(n - 2) + fact(n - 1);
        }
    }
}