#include <fstream>
#include <vector>
std::ifstream fin("nunta.in");
std::ofstream fout("nunta.out");


std::vector <int> a(220);
std::vector <int> b(220);
std::vector <int> c(220);

void plus()
{
	int t(0);
	for (int i = 0; i < 220; ++i)
	{
		c[i] = a[i] + b[i] + t;
		t = c[i] / 10;
		c[i] %= 10;
	}
}

int main()
{
	int n;
	fin >> n;
	if (n == 1)
		fout << "1\n";
	else
	{
		a[0] = b[0] = 1;
		for (int i = 2; i <= n; ++i)
		{
			plus();
			a = b;
			b = c;
		}
		int i = 219;
		while (!c[i])
			--i;
		for (; i >= 0; --i)
			fout << c[i];
		fout << "\n";
	}
	fout.close();
	return 0;
}