#include <iostream>
using namespace std;
int daka(int a)
{
	if (a <= 1)
	{
		return 1;
	}
	else
		return daka(a - 1) + daka(a - 2);
}
int main()
{
	int b;
	cin >> b;
	cout << daka(b);
	return 0;
}