#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <string.h>
using namespace std;
#define all(x) (x).begin(), (x).end()

int N;

long dp[100];

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

int main(){
    cin >> N;
    memset(dp, -1, sizeof(dp));
    cout << move(1) << endl;
}