#include<iostream>
using namespace std;
int n;
int f(int m,int s){
	m+=s;
	if(m==n)return 1;
	if(m>n)return 0;
	return f(m,1)+f(m,2);
}
int main(){
	cin>>n;
	cout<<f(0,1)+f(0,2);
	return 0;
}