#include<stdio.h>
#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<utility>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<functional>
#include<math.h>
#include<random>
#include <bitset>
#include <cassert>
#include <complex>
using namespace std;
//#define N (1000000000+7)
//#define N 998244353
#define INF 1e16
typedef long long ll;
typedef pair<ll,ll> P;
typedef pair<int,P> Q;

ll dp[100];

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