//
// Created by lanys on 2024/4/13.
//
跳台阶
#include <iostream>
using namespace std;
int n;
int answer;
void f(int k) {
if (k == n) answer++;
else if (k < n) {
f(k + 1);
f(k + 2);
}
}
int main() {
cin >> n;
f(0);
cout << answer << endl;
return 0;
}