#include <bits/stdc++.h>
using namespace std;

int main() {
	long long c[9999], n;
	cin >> n;
	c[1] = 1;
	c[2] = 1;
	for (long long int i = 3; i <= n; i++) {
		c[i] = c[i - 2] + c[i - 1];
	}
	for (long long int i = 1; i <= n; i++) {
		if (i == n) {
			cout << c[i];
		}
	}
	return 0;
}