#include <bits/stdc++.h>
#define int long long

using namespace std;

signed main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr); cout.tie(nullptr);
	int n; cin >> n; int f[n+1]; f[0] = f[1] = 1;
	for (int i = 2; i <= n; ++i) f[i] = f[i-1]+f[i-2];
	cout << f[n];
	return 0;
}