Go: package main

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

//util
var sc = bufio.NewScanner(os.Stdin)

func nextStr() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func printList(list []int) {
	buf := bufio.NewWriter(os.Stdout)
	for _, v := range list {
		buf.Write([]byte(fmt.Sprintf(" %d", v)))
	}
	buf.Write([]byte("\n"))
	buf.Flush()
}

//solve
//単純な場合
func fibonacci_(n int) int {
	if n == 0 || n == 1 {
		return 1
	}
	return fibonacci_(n-2) + fibonacci_(n-1)
}

//メモ再帰の利用
func fibonacci(n int) int {
	if n == 0 || n == 1 {
		F[n] = 1
	}
	//F[n]が計算済みの場合
	if F[n] > 0 {
		return F[n]
	}
	F[n] = fibonacci(n-2) + fibonacci(n-1)
	return F[n]
}

const MAX = 50

var F [MAX]int

func main() {
	sc.Split(bufio.ScanWords)
	n := nextInt()
	fmt.Println(fibonacci(n))

}

C++: #include <iostream>
using namespace std;
int main(){
  int n;
  long long int fib1,fib2,fib3;
  cin>>n;
  fib1=1;
  fib2=1;
  if(n==0){
    cout<<0<<endl;
  }else if(n==1){
    cout<<1<<endl;
  }else if(n>=2){
    for(int i=0;i<n-1;i++){
      fib3=fib1+fib2;
      fib1=fib2;
      fib2=fib3;
    }
    cout<<fib3<<endl;
  }
}

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

int main() {
  int n; cin >> n;
  int fib[50];
  fib[0] = fib[1] = 1; //初期条件
  //n>=2のとき
  for ( int i = 2; i <= n; i++ ) {
    fib[i] = fib[i-2] + fib[i-1];
  }

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

C++: #include "bits/stdc++.h"
#include "math.h"
 
using namespace std;
typedef long long ll;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef vector<int> vin;
typedef vector<vin> vvin;
typedef pair<ll,ll> P;
typedef vector<P> vp;
#define rep(i,a,b) for(ll i=(a);i<(b);++i)
#define drep(i,a,b) for(ll i=(a);i>=(b);--i)
#define SIZE(a) int((a).size())
const int MOD=1e9+7;

int main(){
  ll n;cin>>n;
  vll dp(n+1,1);
  rep(i,2,n+1){
    dp[i]=dp[i-2]+dp[i-1];
  }
  cout<<dp[n]<<endl;
}

C++: /**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author champon
 */

#include <iostream>
#include <fstream>
#include<bits/stdc++.h>
#define se cout << "test ok" << endl;
#define sp << " " <<
#define enl "\n"
using namespace std;
using ll=long long;
using ld=long double;
using vi = vector<int>;
using vii = vector<vector<int>>;
using vl = vector<ll>;
using vll = vector<vector<ll>>;
using vc = vector<char>;
using vcc = vector<vector<char>>;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
ll mod = ll(1e9)+7;
ll inf = ll(1e18);
void bl(bool b, ostream& out=cout){ out << (b ? "Yes" : "No") << endl; }
void bl2(bool b, ostream& out=cout){ out << (b ? "YES" : "NO") << endl; }
template<typename T> inline bool chmax(T &a, T b){ if(a<b){a=b; return true;} return false; }
template<typename T> inline bool chmin(T &a, T b){ if(a>b){a=b; return true;} return false; }
int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
int dy[] = {0, 1, 0, -1, 1, -1, -1, 1};

#ifndef INCLUDE_DEBUG_HPP
#define INCLUDE_DEBUG_HPP

#include <iostream>
#include <vector>
#include <map>
using namespace std;

namespace dbg {
    using ll = long long;

    class Debug {
    public:
        Debug(){}
        template<typename T>
        void vd(vector<T> vec);
        template<typename T>
        void vd2(vector<vector<T>> vec);
        template<typename T>
        void ad(T *arr, ll n);
        template<typename T, size_t N>
        void ad2(T (&arr)[N], ll n);
        template<typename T>
        void md(T mp);
    };

    template<typename T>
    void Debug::vd(vector<T> vec) {
        for (auto vv : vec) cout << vv << " ";
        cout << endl;
    }

    template<typename T>
    void Debug::vd2(vector<vector<T>> vec) {
        for (auto vv : vec) {
            for (auto vvv : vv) cout << vvv << " ";
            cout << endl;
        }
    }

    template<typename T>
    void Debug::ad(T *arr, ll n) {
        for (int i = 0; i <= n; i++) cout << arr[i] << " ";
        cout << endl;
    }

    template<typename T, size_t N>
    void Debug::ad2(T (&arr)[N], ll n) {
        for (int i = 0; i <= N; i++) for (int j = 0; j <= n; j++) cout << arr[i][j] << " ";
        cout << endl;
    }

    template<typename T>
    void Debug::md(T mp) {
        cout << "key : value" << endl;
        for (auto const &m : mp) cout << m.first << " : " << m.second << endl;
        cout << endl;
    }

}

#endif //INCLUDE_DEBUG_HPP

using dbg::Debug;
Debug debug;

class a {
public:
	void solve(std::istream& in, std::ostream& out) {
        int n;
        in >> n;
        if(n == 0 || n == 1) {
            out << 1 << enl;
            return;
        }
        vi dp(n+1, 0);
        dp[0] = dp[1] = 1;
        for(int i=1; i<n; i++){
            dp[i+1] = dp[i] + dp[i-1];
        }
//
//        debug.vd(dp);

        out << dp[n] << enl;
	}
};


int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
	a solver;
	std::istream& in(std::cin);
	std::ostream& out(std::cout);
	solver.solve(in, out);
	return 0;
}

C++: #include <bits/stdc++.h>
#define FOR(i, a, b) for (int i = (a), i##_max = (b); i < i##_max; ++i)
#define RFOR(i, a, b) for (int i = (b)-1, i##_min = (a); i >= i##_min; --i)
#define REP(i, n) for (int i = 0, i##_len = (n); i < i##_len; ++i)
#define RREP(i, n) for (int i = (n)-1; i >= 0; --i)
#define ALL(obj) (obj).begin(), (obj).end()

using namespace std;
using vi = vector<int>;
using vd = vector<double>;
using i64 = int64_t;

constexpr int INF = 1 << 30;
constexpr int MOD = 1000000007;

template <typename T>
void print(vector<T> &v) {
  REP(i, v.size()) {
    if (i) cout << " ";
    cout << v[i];
  }
  cout << endl;
}

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

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

int main(int argc, char const *argv[])
{
  int n; cin >> n ;
  int F[50];
  F[0] = F[1] = 1;
  for (int i = 2 ; i < n; ++i)
  {
    F[i] = F[i-1] + F[i- 2];
  }

  cout << F[n] ;

  return 0;
}

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

int F[45];

int fib(int n){
  if (F[n]) return F[n];
  if (n==0||n==1) F[n]=1;
  else F[n]=fib(n-1)+fib(n-2);
  return F[n];
}

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

C++: #include <bits/stdc++.h>
#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;
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 (b<a) {a=b; return 1;} return 0;}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    vector<int> dp(50, 1);
    for (int i = 2; i < 50; ++i) {
        dp[i] = dp[i-1] + dp[i-2];
    }

    int n;
    cin >> n;
    cout << dp[n] << endl;
}

C++: #include <iostream>
#include <vector>
#include <set>
#include <algorithm>
#include <string>
#include <istream>

#define INPUT_FROM_FILE (0)
#if INPUT_FROM_FILE
#include <fstream>
#endif

int main(int argc, char **argv){
#if INPUT_FROM_FILE
	std::ifstream ifs("test.txt");
#endif
	int n = 0;

#if INPUT_FROM_FILE
	ifs >> n;
#else
	std::cin >> n;
#endif
	if(n == 0){
		std::cout << "1" << std::endl;
	}
	else if(n == 1){
		std::cout << "1" << std::endl;
	}
	else{
		int pp = 1;
		int p = 1;
		int ans = 0;

		for(int i = 2; i <= n; i++){
			ans = p + pp;

			pp = p;
			p = ans;
		}
		std::cout << ans << std::endl;
	}
	return 0;
}

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

int main(){
    int n;
    cin >> n;
    int dp[n+1];
    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;
}