#include <iostream>
#include <vector>

using namespace std;

int main() {
	int n;
	cin >> n;
	vector<long long> patterns(n + 1);
	patterns[0] = 1LL;
	patterns[1] = 1LL;
	for (int i = 2; i <= n; ++i) {
		patterns[i] = patterns[i - 2] + patterns[i - 1];
	}
	cout << patterns[n] << endl;
	return 0;
}