Go: package main

// import (
// 	"fmt"
// 	"bufio"
// 	"strconv"
// 	"os"
// )

// func fib(n int) int{
// 	if n == 0 || n == 1{
// 		return 1
// 	} else {
// 		return fib(n-1) + fib(n-2)
// 	}
// }

// func main(){
// 	sc := bufio.NewScanner(os.Stdin)
// 	sc.Scan()
// 	n, _ := strconv.Atoi(sc.Text())
// 	fmt.Println(fib(n))
// }

import (
	"fmt"
)

func main(){
	var n, pre1, pre2, now int
	fmt.Scan(&n)
	if n == 0 || n == 1{
		fmt.Println(1)
	} else {
		pre1, pre2 = 1, 1
		for i:=1; i<n; i++{
			now = pre1 + pre2
			pre2 = pre1
			pre1 = now
		}
		fmt.Println(now)
	}

}

C++: #include <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <string>
#include <cstring>
#include <complex>
#include <ctime>
#include <cstdlib>

using namespace std;

inline int to_int(string s) {int v; istringstream sin(s); sin >> v; return v;}
template<class T> inline string to_str(T x) {ostringstream sout; sout << x; return sout.str();}

typedef long long ll;

int main()
{
	int fib[1256], num;

	fib[0] = 1; fib[1] = 1;

	for(int i = 2; i < 128; i++)
	{
		fib[i] = fib[i-1] + fib[i-2];
	}
	cin >> num;

	cout << fib[num] << endl;
}

C++: #include <cstdio>
#include <iostream>
#include <algorithm>
using namespace std;
int A[50];
int fib(int n){
	if(n==1 || n==0) A[n]=1;
	
	else if(A[n]) ;
	else A[n]=fib(n-1)+fib(n-2);
	return A[n];
}

int main (){
	int n;
	cin>>n;
	cout<<fib(n)<<endl;
	return 0;
}

C++: #include<iostream>

using namespace std;

int main() {
  int N;
  cin >> N;

  int F[50];

  F[0] = F[1],
  for (int i = 2; i <= N; i++) {
    F[i] = F[i - 1] + F[i - 2];
  }

  cout << F[N] << endl;

  return 0;
}

C++: //
// Created by miyoshi on 2019/05/23.
//

#include <iostream>

using namespace std;

int N[45];


int f(int n) {
    if (N[n] != 0) {
        return N[n];
    }
    else if (n==0 || n==1) {
        return 1;
    } else {
        return f(n-1) + f(n-2);
    }
}

int main() {
    int n;
    cin >> n;

    for (int i=0; i <= n; i++) {
        N[i] = 0;
    }

    for (int i=0; i <= n; i++) {
        N[i] = f(i);
    }

    cout << N[n] << endl;
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

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

C++: #include <iostream>

using namespace std;
int d[45];
int main(){
    int n;
    cin>>n;
    d[0]=d[1]=1;
    for(int i=2;i<=n;i++){
        d[i]=d[i-1]+d[i-2];
    }
    cout<<d[n]<<endl;
    return 0;
}

C++: #include <iostream>
#include <cstring>
#include <cstdlib>
#include <sstream>
#include <stack>
#include <queue>
#include <list>
#include <stdio.h>
#include <algorithm>
#define MAX 100000
using namespace std;
typedef long long ll;
int dp[50];
int main()
{	
	int n;
	cin>>n;
	dp[0]=dp[1]=1;
	for(int i=2;i<=n;i++) dp[i]=dp[i-1]+dp[i-2];
	cout<<dp[n]<<endl;
	return 0;
}

C++: #include "bits/stdc++.h"

using namespace std;

int main (){
	int n;
	cin >> n;
	int a[44];
	a[0] = 1;
	a[1] = 1;
	for (int i = 2;i<=n;i++){
		a[i] = a[i - 1] + a[i - 2];
	}
	cout << a[n - 1]<<endl;


	return 0;
}

C++: #include <iostream>
#include <vector>
using namespace std;

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

C++: #include<algorithm>
#include<iostream>
using namespace std;

int fib[44],n;
int main() {
  fib[0] = 1;
  fib[1] = 1;
  for (int i = 1; i <= 44; ++i) {
	if (i >= 2) fib[i] = fib[i-1] + fib[i-2];
	}
	cin >> n;
	cout << fib[n] << endl;
	}

C++: #include<iostream>
using namespace std;

int Fibonacci(int n)
{
	if (n == 0 || n == 1) return 1;
	return Fibonacci(n - 1) + Fibonacci(n - 2);
}

int main()
{
	int n;
	cin >> n;
	cout << Fibonacci(n) << endl;
	return 0;
}

C++: #include<iostream>
using namespace std;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);

	int n, N[50];
	N[0] = N[1] = 1;
	cin >> n;

	for (int i = 2; i <= n; i++)
		N[i] = N[i - 1] + N[i - 2];

	cout << N[n];
	return 0;
}

C++: //
// Created by Sotetsu KOYAMADA on 2020/03/02.
//

#include <iostream>
#include <vector>

int fib(int n, std::vector<int> &dp) {
    if (n == 0) return 1;
    if (n == 1) return 1;
    if (dp[n] != -1) return dp[n];
    return dp[n] = fib(n - 1, dp) + fib(n - 2, dp);
}

int main() {
    int n;
    std::cin >> n;
    std::vector<int> dp(n+1, -1);
    std::cout << fib(n, dp) << std::endl;
}

C++: #define LOCAL
#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<(n); ++i)
#define rrep(i, n) for(int i=(n-1); i>=0; --i)
#define rep2(i, s, n) for(int i=s; i<(n); ++i)
#define ALL(v) (v).begin(), (v).end()
#define memr(dp, val) memset(dp, val, sizeof(dp))
using namespace std;
typedef long long ll;
static const int INTINF = (INT_MAX >> 1); // 10^9 + 10^7
static const ll LLINF = (LLONG_MAX >> 1);
static const int MAX = 1e5+1;
static const ll MOD = 1e9+7;
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; }
string to_string(string s) { return '"' + s + '"'; }
string to_string(bool b) { return b ? "true" : "false"; }
template <size_t N> string to_string(bitset<N> bs) {
  string res;
  for (size_t i = 0; i < N; ++i) res += '0' + bs[i];
  return res;
}
string to_string(vector<bool> v) {
  string res = "{";
  for (bool e : v) res += to_string(e) + ", ";
  return res += "}";
}
template <class T, class U> string to_string(pair<T, U> p);
template <class C> string to_string(C c) {
  string res = "{";
  for (auto e : c) res += to_string(e) + ", ";
  return res += "}";
}
template <class T, class U> string to_string(pair<T, U> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
void debug() { cerr << '\n'; }
template <class Head, class... Tail> void debug(Head head, Tail... tail) {
  cerr << '\t' << to_string(head), debug(tail...);
}
#ifdef LOCAL
#define DEBUG(...) cerr << "[" << #__VA_ARGS__ << "]:", debug(__VA_ARGS__)
#else
#define DEBUG(...)
#endif

ll dp[100];
int main(int argc, const char * argv[]) {
	std::cout << std::fixed << std::setprecision(15);

	memr(dp, 0);
	int n; cin >> n;
	dp[0] = 1;
	dp[1] = 1;
	rep(i, 50){
		dp[i+2] = dp[i] + dp[i+1];
	}
	cout << dp[n] << endl;
}