Go: package main

import (
	"fmt"
)

const MAX = 45

var dp [MAX]int

func fin(n int) int {
	if dp[n] != 0 {
		return dp[n]
	}

	switch n {
	case 0:
		dp[n] = 1
	case 1:
		dp[n] = 1
	default:
		dp[n] = fin(n-1) + fin(n-2)
	}
	return dp[n]
}

func main() {
	var n int
	fmt.Scan(&n)
	fmt.Println(fin(n))
}

C++: #include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef vector<ld> vd;
typedef vector<ll> vll;
typedef vector<string> vstr;
typedef vector<vector<ll>> vvll;
typedef vector<pair<ll, ll>> vpll;
typedef priority_queue<ll, vector<ll>, greater<ll>> spqll;  // 小さい順に取り出し
typedef priority_queue<ll, vector<ll>, less<ll>> bpqll;     // 大きい順に取り出し

#define REP(i, n) for (ll i = 0; i < (ll)(n); i++)
#define FOR(i, a, b) for (ll i = (ll)a; i < (ll)b; i++)
#define IREP(i, v) for (auto i = (v).begin(); i != (v).end(); i++)
#define FI first
#define SE second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define TS to_string
#define NP next_permutation
#define ALL(v) (v).begin(), (v).end()
#define SZ(x) (ll) x.size()
#define SP(x) setprecision((ll)x)


ll INF = 1e9;
ll NIL = -1;
ll MOD = 1000000007;
ll LINF = 1e18;
ld EPS = 1e-9;
ld PI = M_PI;
vll dx = {1, 0, -1, 0, 1, -1, -1, 1};
vll dy = {0, 1, 0, -1, 1, 1, -1, -1};
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a;} //最大公約数
ll lcm(ll a, ll b) { return a / gcd(a, b) * b;}     //最小公倍数

void yes(){ cout << "yes" << endl;}
void no(){ cout << "no" << endl;}

//-----------------------------------------

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

  int n;
  cin >> n;
  vll fib(100);
  fib[0] = 1;
  fib[1] = 1;
  for(int i=2;i<=n;i++){
    fib[i] = fib[i-1] + fib[i-2];
  }
  cout << fib[n] <<endl;




  return 0;
}

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

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

C++: #include <iostream>
#include <algorithm> // next_permutation
#include <iomanip>
#include <cmath>
#include <vector>
#include <sstream>
#include <string>
#include <cstdio>
#include <stack>
#include <queue>
#include <list>
#include <numeric> //accumulate
//#include <unordered_map> //???????????\??¢??°
#include <fstream> //ifstream, ofstream

//#define NDEBUG //NDEBUG???#include <cassert>???????????????????????????????????´???assert?????????????????????????????????NDEBUG?????????????????????????????????????????????
#include <cassert> //assert


using namespace std;

//???????????°??????TEST????????????????????¬???????????????????????????????????¢????????????
#define TEST //*******************************************************************************************************************************************
//?????????????????¨??§?????\????????????????????????????????°?????????????¨???????????????????dout???????????????????????§???????????¬??????????????????????????????????????????
//??????????????????????????????????????????????????????????§?CPU???????£??????????????????§???TLE?????????????????????????????????????????§????????¨???                           ????????????????????????cerr????????£????????????????????????????????????
#ifdef TEST
#define dout cout
#define din cin
#else
stringstream dummy; //???????????°??????dout?????????????????????????????????
#define dout dummy.str(""); dummy.clear(stringstream::goodbit); dummy //dummy?????????????????????????????????????????¨?????¢?????¢???????????????
//???????????¨??????????????????goodbit?????????????????????????????¨???????????´????????????????????????????????¨?????°?????????????????§???????????????????????????????????? http://d.hatena.ne.jp/linden/20060427/p1
#endif

//?¨??????????????????????????????????????????????????????´??????OUTPUTFILE????????????????????¬???????????????????????????????????¢????????????
//#define OUTPUTFILE "output.txt" //*******************************************************************************************************************************************
#ifdef OUTPUTFILE
#define dout outputfile //??¨????????????TLE????????§?????????dout?????¨??¨??????????????¢????????????????????????????????????????????§????¨????????????´??????????????£??????????????????????¨?????????????????????????????????????????????§?????????????????????
ofstream outputfile(OUTPUTFILE);
#define OutputFilePath "/Users/Nag/Documents/Prgm/Test/DerivedData/Test/Build/Products/Debug/output.txt"
#endif

//?¨??????\???????????????????????????????????????????????´??????INPUTFROMTEXTFILE????????????????????¬???????????????????????????????????¢????????????
//#define INPUTFILE "input.txt" //*******************************************************************************************************************************************
#ifdef INPUTFILE
#define din inputfile
ifstream inputfile(INPUTFILE);
#endif


#define disp(A) dout << #A << " = " << (A) << endl
#define disP(A) dout << setw(3) << (A) << " " // << setw(3) ??????????????\????????????
#define rep(i,a,n) for(int (i)=(a); (i)<(n); (i)++)

#define dispAll(A,n) dout << #A << " = "; rep(j, 0, (n)) {disP(A[j]);} dout << endl

typedef pair<int,int> pii;
typedef vector<int> vi;
typedef unsigned long long ll;

const int INF = 1e9-1;

int F[45] = {0};

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


int main() {
    int n; cin >> n;
    
    dout << fibonacci(n) << endl;
    
    
    
#ifdef INPUTFILE
    inputfile.close();
#endif
    
#ifdef OUTPUTFILE
    outputfile.close();
    cout << "\"" << OutputFilePath << "\"" << endl;
#endif
    
    return 0;
}

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

int fib(int n)
{
	int f[45];
	if(n==0 || n==1) return f[n]=1;
	if(f[n]>0) return f[n];
	return f[n]=fib(n-1)+fib(n-2);;
}

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

C++: #include <iostream>
#include<algorithm>
#include<stack>
#include<string>
#include<cstdlib>
#include<stdio.h>
using namespace std;
int n,a[50];
int solve(int i){
    if(i==1||i==0)return 1;
    return solve(i-1)+solve(i-2);
}
int main(){
    int n;
    cin>>n;
    int ans[50];
    ans[0]=1,ans[1]=1;
    for(int i=2; i<=n; i++){
        ans[i]=ans[i-1]+ans[i-2];
    }
    cout<<ans[n]<<endl;
    return 0;
}