#include <bits/stdc++.h>
#include <iostream>
using namespace std;
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define rep(i,a,b) for(LL i = a;i<b; i++)
#define rrep(i,a,b) for(LL i = a;i>b; i--)
#define tobirep(i,a,b,c) for(LL i = a;i<b; i+=c)
#define tobirrep(i,a,b,c) for(LL i = a;i>b; i-=c)
#define INF ((1LL<<62)-(1LL<<31))
#define ooki 9223372036854775807
#define tii -9223372036854775808
#define MOD 1000000007
typedef long long LL;
int main(){  
 ios::sync_with_stdio(0);cin.tie(nullptr);
  LL n;
  cin >> n;
  vector<LL> dp(n+100);
  dp[0]=1;
  dp[1]=1;
  rep(i,2,n+1){
    dp[i]=dp[i-2]+dp[i-1];
  }
  cout << dp[n] << '\n';
}