#include <bits/stdc++.h>

#define REP(i, n) for (int i = 0; i < n; i++)
#define llINF ((long long)1e18)
#define INF ((int)1e9);
#define ALL(obj) obj.begin(), obj.end()

using namespace std;

int N;

int rec(int n) {
    if (n > N) return 0;
    if (n == N) return 1;
    int res = rec(n + 1) + rec(n + 2);
    return res;
}

int main() { 
    cin >> N;
    cout << rec(0) << endl;
}