import java.util.Scanner;

public class Main {
	public static int[] F = new int[51];
	public static int numberOfWays(int n){
		F[0] = 0;
		F[1] = 1;
		F[2] = 1;
		F[3] = 2;
		F[4] = 3;
	    if(F[n] > 0) {
    		return F[n];
		} else {
    		F[n] = numberOfWays(n-2) + numberOfWays(n-3) + numberOfWays(n-4);
		}
		return F[n];
	}
	public static void main (String[] args){
	    Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
	    System.out.println(numberOfWays(n));
	}
}