/*
 * recurrence-relations.c
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

unsigned long f_arr [100], g_arr [100];

unsigned long 
f (int n);

unsigned long 
g (int n);


int
main (void)
{
	char s [100];
	int n, i;

	for (i = 0; i < 100; i++)
		f_arr [i] = g_arr [i] = -1;

	f_arr [1] = 1;
	g_arr [1] = g_arr [3] = 1;
	g_arr [2] = 0;

	while (gets (s) != NULL) {
		sscanf (s, "%d", &n);
		printf ("%lu\n", f (n));
	}

	return 0;
}

unsigned long 
f (int n)
{
	if (n == 1)
		return 1;

	if (f_arr [n] == -1)
		f_arr [n] = f (n - 1) + g (n - 1);

	return f_arr [n];
}

unsigned long 
g (int n)
{
	if (n == 1)
		return 1;
	else if (n == 2)
		return 0;
	else if (n == 3)
		return 1;

	if (g_arr [n] == -1)
		g_arr [n] = g (n - 1) + g (n - 3);

	return g_arr [n];
}