#include <atcoder/all>
#include <bitset>
#include <fstream>
#include <functional>
#include <iostream>
#include <iomanip>
#include <limits>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdio.h>
#include <stdlib.h>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;
using namespace atcoder;

typedef long long ll;
typedef long double ld;
typedef std::pair<int, int> pii;
typedef std::pair<ll, ll> pll;
typedef std::pair<ld, ld> pid;
typedef std::pair<ll, std::string> pls;
typedef std::vector<bool> vb;
typedef std::vector<vb> vvb;
typedef std::vector<int> vi;
typedef std::vector<vi> vvi;
typedef std::vector<vvi> vvvi;
typedef std::vector<vvvi> vvvvi;
typedef std::vector<ll> vl;
typedef std::vector<vl> vvl;
typedef std::vector<vvl> vvvl;
typedef std::vector<vvvl> vvvvl;
typedef std::vector<ld> vd;
typedef std::vector<vd> vvd;
typedef std::vector<std::string> vs;
#define rep(i,n) for(auto i=0; i<n; ++i)
#define repm(i,s,n) for(auto i=s; i<n; ++i)
#define repd(i,n) for(auto i=n-1; i>=0; --i)
#define repdm(i,e,n) for(auto i=n-1; i>=e; --i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()

template <class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template <class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

template <class mint, internal::is_modint_t<mint>* = nullptr> constexpr istream& operator>>(istream& is, mint& x) noexcept {long long v = 0; std::cin >> v; x = v; return is;}
template <class mint, internal::is_modint_t<mint>* = nullptr> constexpr ostream& operator<<(ostream& os, const mint& x) noexcept {os << x.val(); return os;}
inline void _n() { std::cout << std::endl; }
template <class T> inline void _(const T a) { std::cout << a; }
template <class T> inline void _l(const T a) { _(a); _n(); }
template <class T> inline void _s(const T a) { _(a); _(' '); }
template <class T> inline void _v(const std::vector<T> v) { for(auto a : v) _(a); }
template <class T> inline void _vl(const std::vector<T> v) { for(auto a : v) _l(a); }
template <class T> inline void _vs(const std::vector<T> v) { for(auto a : v) _s(a); _n(); }
template <class T> inline void _vvl(const std::vector<std::vector<T>> v) { for(auto a : v) { _v(a); _n(); } }
template <class T> inline void _vvs(const std::vector<std::vector<T>> v) { for(auto a : v) { _vs(a); } }
inline void ynl(const bool b) {_l(b ? "yes" : "no");}
inline void yns(const bool b) {_l(b ? "Yes" : "No");}
inline void ynu(const bool b) {_l(b ? "YES" : "NO");}

constexpr int INF = numeric_limits<int>::max() >> 1;
constexpr long long INF_LL = numeric_limits<long long>::max() >> 1LL;
const long long MOD1 = 1000000007;
const long long MOD9 = 998244353;
using mint1 = atcoder::modint1000000007;
using mint9 = atcoder::modint998244353;


//* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *//

void input() {
    
    
}


void solve() {
   
    
    int N; cin >> N;
    
    vl dp(N+1);
    dp[0] = dp[1] = 1;
    repm(i, 2, N+1) dp[i] = dp[i-1] + dp[i-2];
    _l(dp[N]);
    
 
    
}

//* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *//

int main() {
    
    std::ifstream in("input.txt");
    std::cin.rdbuf(in.rdbuf());
    std::cin.tie(0);
    ios::sync_with_stdio(false);
    
    input();
    solve();
    
    return 0;
}