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 <iostream>
using namespace std;

typedef unsigned long long ull;
int dp[45] = {0};

ull fib(int n) {
  // ???????????????
  if(dp[n] != 0)return dp[n];
  if(n == 1 || n == 0)return 1;
  return dp[n] = fib(n - 2) + fib(n - 1);
}

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

C++: #include<iostream>

using namespace std;
int fib(int n);
int main() {
  int n;

  //入力
  cin >> n;

  //出力
  cout << fib(n) << endl;

  return 0;
}

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

C++: #include <iostream>
#include <map>
using namespace std;
int memofib(int n) {
    static map<int,int> cache;
    map<int,int>::iterator it = cache.find(n);
    if( it != cache.cend() )
        return it->second;   
    int t;
    if(n==1) 
        return 1;
    else if(n==2)
        return 2;
    else
        return memofib(n-1) + memofib(n-2);
    cache.insert(std::make_pair(n, t));
    return t;
}
int main(void){
    int n;
    cin >> n ;
    cout << memofib(n) << endl;
    return 0;
}

C++: #include<iostream>
using namespace std;
int data[45];
int fib(int n){
  if(data[n]) return data[n];
  if(n==0||n==1) return data[n]=1;
  return data[n]=fib(n-1)+fib(n-2);
}
int main(){
  int n; cin>>n;
  cout<<fib(n)<<endl;
  return 0;
}

C++: #include<stdio.h>

int main(){
  int i,input,fibonacciA=1,fibonacciB=1,fibonacciC=1;
  scanf("%d",&input);
  if(input == 0 || input == 1){
    printf("%d\n",fibonacciA);
  }else{
    for(i=1;i<input;i++){
      fibonacciC = fibonacciB + fibonacciA;
      fibonacciA = fibonacciB;
      fibonacciB = fibonacciC;
    }
    printf("%d\n",fibonacciC);
  }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define REP(i,s,n) for(int i=s;i<n;i++)
#define all(a) a.begin(),a.end()
typedef long long ll;
const double phi = (1 + sqrt(5)) / 2;
const double phi_ = (1 - sqrt(5)) / 2;
double fib(ll n){
    double res = pow(phi, n+1) - pow(phi_, n+1);
    return res / sqrt(5);
}
int main(){
    ll n, ans; cin >> n;
    ans = fib(n);
    cout << ans << endl;
    return 0;
}

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

int main(){
    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] << endl;
    
    return 0;
}

C++: #include <cstdio>
#include <iostream>

using namespace std;

int F[50];

int fib(int n) {

	if (n == 0 || n == 1)
		return 1;
	if (F[n] != 0)
		return F[n];

	F[n] = fib(n - 1) + fib(n - 2);

	return F[n];
}

int main() {

	int n;
	scanf("%d", &n);

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

	cout << fib(n) << endl;

	return 0;

}

C++: #include "stdio.h"

#define MAX 50
#define INIT -1

int dp[MAX];

int fibonacci(int n){
  if(n == 0 || n == 1){
    return dp[n] = 1;
  }

  if(dp[n] >= 0 ){
    return dp[n];
  }else{
    return dp[n] = fibonacci(n-1) + fibonacci(n-2);    
  }
}


int main(void){
  
  int N;
  scanf("%d", &N);
  
  for(int i=0;i<MAX;i++){
    dp[i] = INIT;
  }
    
  printf("%d\n", fibonacci(N));

  return 0;
}

C++: #line 1 "/mnt/c/Users/leafc/dev/compro/lib/template.hpp"


#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; i < n; i++)
#define FOR(i, m, n) for (int i = m; i < n; i++)
#define ALL(v) (v).begin(), (v).end()
#define coutd(n) cout << fixed << setprecision(n)
#define ll long long int
#define vl vector<ll>
#define vi vector<int>
const int INF = 2147483647;
const ll MOD = 1000000007;

using namespace std;


#line 2 "tmp.cpp"

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

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

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

int fib(int n){
    if(n <= 1)
        return 1;
    else
        return fib(n-1) + fib(n-2);
}