#include <iostream>
#include <algorithm>
using namespace std;

int N;
long dp[50];

long move(int now){
    if(now >= N){
        return now == N;
    }else if(dp[now] != -1){
        return dp[now];
    }else{
        return dp[now] = move(now + 1) + move(now + 2);
    }
}

int main(){
    cin >> N;
    fill(dp, dp + 50, -1);
    cout << move(0) << endl;
}