#include<iostream>
#include<fstream>
using namespace std;
int main()
{
	ifstream f("kfib.in");
	ofstream g("kfib.out");
	long i=2, k,a,b,sum=0;
	a = b = 1;
	f >> k;
	if (k >= 3){
		while (k != i)
		{
			sum = a + b;
			b = a;
			a = sum;
			i++;
		}
	}
else
	sum = 1;
	g << sum;

	
	f.close();
	g.close();
	return 0;
}