#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <cstring>

typedef long long ll;
using namespace std;

#define mod 1000000009
#define INF 10000000
#define LLINF 2000000000000000000LL

#define SIZE 10001

int main(){
    int n;
    ll dp[102]={0},ans=0;
    
    scanf("%d",&n);
    
    dp[0]=1;
    
    for(int i=0;i<n;i++){
        dp[i+1]+=dp[i];
        dp[i+2]+=dp[i];
    }
    
    printf("%lld\n",dp[n]);
    
    return 0;
}