#include <iostream>
#include <fstream>
#include <map>

int main(int argc, char* argv[])
{
	std::ifstream input("kfib.in");
	std::ofstream output("kfib.out");

	int K;
	input >> K;
	int f1 = 1;
	int f2 = 1;
	int f3;
	for ( int i = 2; i < K; ++i )
	{
		f3 = f2 + f1;
		f1 = f2;
		f2 = f3;
	}
	output << f3 << std::endl;

	input.close();
	output.close();
	return 0;
}