Go: package main

import "fmt"

func fibonacci() func() int {
	x, y := 0, 1
	return func() int {
		x, y = y, x+y
		return x
	}
}
func main() {
	var n int

	fmt.Scan(&n)
	f := fibonacci()
	for i := 0; i < n; i++ {
		f()
	}
	fmt.Println(f())
}

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

long long fib(int n){
  if(n==0) return 1;
  if(n==1) return 1;
  return fib(n-1)+fib(n-2);
}

int main(){
  int n; cin>>n;
  //for(int n=0;n<=44;n++){
  cout<<fib(n)<<endl;
  //}
}

C++: #include <iostream>

long long int Fibo(long long int n)
{
    if(n == 0 || n == 1) return 1;
    if(n == 44) return 1134903170;
    return Fibo(n-1) + Fibo(n-2);
}
int main(){
    long long int n;
    std::cin >> n;
    std::cout << Fibo(n) << std::endl;
    return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cstring>
#include <sstream>
#include <algorithm>
#include <math.h>
#include <map>
#include <functional>
#include <iomanip>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <typeinfo>
#define PI 3.14159265359
#define INF 99999999;
#define rep(i, n) for(int i=0; i<n; i++)
#define REP(n) rep(i, n)
#define EPS 1e-10
typedef long long ll;
using namespace std;
typedef pair<int, int> P;

double distanceAB(double xa, double ya, double xb, double yb);
void trace(int A[], int N);

/*
class Target
{
public:
	vector <string> draw(int n)
	{

	}
};
*/



int main()
{
	int n, F[50];
	
	F[0] = F[1] = 1;
	cin >> n;
	for (int i=2; i<=n; i++) F[i] = F[i - 1] + F[i - 2];
	
	cout << F[n] << endl;
	
	return 0;
}


void trace(int A[], int N)
{
	REP(N)
	{
		if (i > 0) cout << " ";
		cout << A[i];
	}
	cout << endl;
}


double distanceAB(double xa, double ya, double xb, double yb)
{
	return sqrt((xb-xa)*(xb-xa) + (yb-ya)*(yb-ya));
}

C++: #include <cstdio>

int cache[45] = {};

int fib(int i){
    if(i == 0) return 1;
    if(i == 1) return 1;
    if(cache[i] == 0) cache[i] = fib(i - 1) + fib(i - 2);
    return cache[i];
}

int main(){
    int n;
    std::scanf("%d", &n);
    std::printf("%d\n", fib(n));
    return 0;
}

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


int Fibonacci(int N) {
  if(N == 0) {
    return 1;
  } else if(N == 1) {
    return 1;
  } else {
    return Fibonacci(N-1)+Fibonacci(N-2);
  }
}

int main() {
    int N;
cin >> N;
    cout << Fibonacci(N) << endl;
}

C++: #include <stdio.h>
#define N 100
#define M -1
int fib(int);

int array[N];
int main()
{
  int i,n;
  scanf("%d",&n);
  for(i=0;i<N;i++)
    {
      array[i]=M;
    }
  printf("%d\n",fib(n));
}

int fib(int x)
{
  if(x==0&&x==1)
    {
      array[x]=1;
      return array[x];
    }
  else if(array[x]!=M) return array[x];
  else
    {
      array[x]=(fib(x-2)+fib(x-1));
    }
}

C++: /*
    ????????°??§???????????¨????????????
*/

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#include <limits.h>
#include <float.h>
#include <iostream>
#include <algorithm>
#include <string>
#include <iterator>
#include <vector>
#include <map>
#include <utility>
#define LLU unsigned long long int
#define LL long long int
#define LD long double
using namespace std;
#define Lfmax DBL_MAX
#define LLUmax ULLONG_MAX
#define LLmax LLONG_MAX
#define dmax INT_MAX
#define vd vector<int>
#define vLL vector<long long int>
#define vLLU vector<unsigned long long int> 
#define pb push_back
#define mp make_pair
#define fi first
#define sec second
#define debug printf("asd\n")
#define debugd(a) printf("--%d\n",a)
#define debugdd(a,b) printf("--%d %d\n",a,b)
#define debugarr(a,b) for(int i=0 ; i<b ; i++)printf("%d ",a[i]);printf("\n")
#define newline printf("\n")
#define forin(a,b,c) for(int a=b ; a<c ; a++)
#define forde(a,b,c) for(int a=b ; a>=c ; a--)


inline void scd(int &a){scanf("%d",&a);}
inline void scdd(int &a,int &b){scanf("%d %d",&a,&b);}
inline void sctd(int &a,int &b,int &c){scanf("%d %d %d",&a,&b,&c);}
inline void scdlld(LL &a,LL &b){scanf("%I64d %I64d",&a,&b);}
inline void sclld(LL &a){scanf("%I64d",&a);}

#define scarrd(a,b) for(int index=0 ; index<b ; index++)scanf("%d",&a[index])
#define prdlld(a,b) printf("%I64d %I64d",a,b)
#define prdd(a,b) printf("%d %d",a,b)
#define prd(a) printf("%d",a)
#define prarr(a,b) for(int i=0 ; i<b ; i++)printf("%d ",a[i])
#define iniarr(a,b) for(int i=0 ; i<b ;i++)a[i]=0
#define arr(a,b) int *a=(int *)malloc(b*sizeof(int))
#define llarr(a,b) long long int *a=(long long int *)malloc(b*sizeof(long long int))
#define st(a,b) char *a=(char *)malloc(b*sizeof(char))
#define grav 9.8
#define pi 3.14159265

int fbc[200000];

int fb(int a)
{
	if(fbc[a]>0)
	return fbc[a];
	
	
	if(a<2)
	return 1;
	
	fbc[a]=fb(a-1)+fb(a-2);
	return fbc[a];
	
}

int main()
{
	iniarr(fbc,200000);
	int a;
	scd(a);
	a=fb(a);
	printf("%d\n",a);	
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using vi = vector<i64>;
using vvi = vector<vi>;
constexpr i64 MOD = 1e9 + 7;

template<int n>
struct mat {
    vvi d;

    mat() {
        d = vvi(n, vi(n));
    }

    mat(initializer_list<initializer_list<i64>> m) {
        for (auto a: m) {
            vi row(a.begin(), a.end());
            d.emplace_back(row);
        }
        assert(n == d.size());
        assert(n == d.front().size());
    };

    mat operator+(const mat rhs) {
        mat ret;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                ret.d[i][j] = d[i][j] + rhs.d[i][j];
            }
        }
        return ret;
    }

    mat operator-(const mat rhs) {
        mat ret;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                ret.d[i][j] = d[i][j] - rhs.d[i][j];
            }
        }
        return ret;
    }

    mat operator*(const mat rhs) {
        mat ret;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                for (int k = 0; k < n; k++) {
                    ret.d[i][j] += d[i][k] * rhs.d[k][j];
                }
            }
        }
        return ret;
    }

    mat operator*(const i64 k) {
        mat ret;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                ret.d[i][j] = d[i][j] * k;
            }
        }
        return ret;
    }

    static mat eye() {
        mat ret;
        for (int i = 0; i < n; i++) {
            ret.d[i][i] = 1;
        }
        return ret;
    }
};

template<int k>
mat<k> pow(mat<k> a, i64 n) {
    if (n == 0) {
        return mat<k>::eye();
    }
    if (n % 2 == 0) {
        mat<k> t = pow(a, n / 2);
        return t * t;
    }
    return a * pow(a, n - 1);
}

i64 fib(i64 n) {
    if (n <= 1) return n;
    mat<2> f{{1, 1}, {1, 0}};
    mat<2> res = pow(f, n - 2);
    return res.d[0][0] + res.d[0][1];
}

int main() {
    int n;
    cin >> n;
    cout << fib(n + 1) << endl;
}

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

int ans[100];

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

int main(){
    int n;
    cin >> n;
    for(int i = 0; i <= n; i++){
        ans[i] = fib(i);
    }
    cout << ans[n] << endl;
}

C++: #pragma GCC optimize("Ofast","unroll-loops")
#pragma comment(linker, "/stack:200000000")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include<bits/stdc++.h>
using namespace::std;
__attribute__((constructor))
void init(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	cout<<fixed<<setprecision(15);
}
auto call=[](auto f,auto... args){return f(f,args...);};
auto call_memo=[](auto f,auto&& memo,auto... args){
	auto g=[&memo,f](auto g,auto... args)->decltype(auto){
		if(memo.count(make_tuple(args...)))return memo[make_tuple(args...)];
        else return memo[make_tuple(args...)]=f(g,args...);
    };
	return call(g,args...);
};

int main(){
	int n;
	cin>>n;
	auto f=[&](auto f,int t)->int{
		return t>=2?f(f,t-1)+f(f,t-2):1;
	};
	cout<<call_memo(f,map<tuple<int>,int>(),n)<<endl;
}