#include<bits/stdc++.h>
using namespace std;
int f(int n)
{
	int r;
	if(n==1 || n==2)
	{
		r=1;
	}
	else
	{
		r=f(n-1)+f(n-2);
	}
	return r;
}
int main()
{
	int n;
	cin>>n;
	cout<<f(n);
	return 0;
}

/**************************************************************
	Problem: 1238
	User: chenkexin
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2072 kb
****************************************************************/