#include<bits/stdc++.h>
using namespace std;
int ss(int n){
	int a;
	if(n<3){
		a=1;
	}else{
		a=ss(n-1)+ss(n-2);
	}
	return a;
}
int main()
{
	int a,i,n;
	cin>>n;
	a=ss(n);
	cout<<a;
	return 0;
}

/**************************************************************
	Problem: 1238
	User: zzz
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2072 kb
****************************************************************/