#include <iostream>
#include <iomanip>
#include <stack>
#include <queue>
#include <vector>
#include <algorithm>
#include <map>
#include <set>
using namespace std;

int main() {
    int n;
    cin >> n;
    vector<long long> dp(n + 10, 0);

    dp[0] = 1;
    for(int i = 0; i < n; i++){
        dp[i + 1] += dp[i];
        dp[i + 2] += dp[i];
    }
    cout << dp[n] << endl;
}