#include<fstream>
using namespace std;

int k;

int fib(){
	int a=0,b=1,c,i;
	for(i=2;i<=k;i++){
		c=a+b;
		a=b;
		b=c;
	}
	return c;
}

int main(){
	ifstream in("kfib.in");
	ofstream out("kfib.out");
	in>>k;
	out<<fib();
	out.close();
	return 0;
}