#include <iostream>
using namespace std;

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

int main() {
	int n;
	cin >> n;
	
	cout << fib(n) << endl;
	return 0;
}