#include<iostream>
using namespace std;

int n,res;

void dfs(int num)
{
    if(num>n)
    return;
	if(num==n)
	{
		res++;
		return;
	}
	dfs(num+1);
	dfs(num+2);	
}

int main()
{
	while(cin>>n)
	{
		res=0;
		dfs(0);
		cout<<res<<endl;
	}
}