#include<bits/stdc++.h>
using namespace std;

int f(int n)
{
	if(n <= 3) return 1;
	return f(n - 1) + f(n - 2);
}

int main()
{
	int n;
	cin >> n;
	cout << f(n) << endl;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
int f(int n) {
	if(n<=3) return 1;
	return f(n-1) + f(n-2);
	
}
int main()
{
	int n;
	cin>>n;
	cout<<f(n)<<endl;
}