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++: // Algorithms and Data Structures 1
// Fibonacci Numbers
// Name: Ryuya Asada
// ID: s1260064

#include <iostream>

int fibonacci(int);

int main() {
    int n(0);
    std::cin >> n;

    std::cout << fibonacci(n) << "\n";

    return 0;
}

int fibonacci(int n) {
    int a(0), b(1), c(1);
    for(int i=1; i <= n; ++i) {
        c = a + b;
        a = b;
        b = c;
    }

    return c;
}

C++: #include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define rep(i,n) for (int i=0;i<(int)(n);i++)
#define codefor int test;scanf("%d",&test);while(test--)
#define yn(ans) if(ans)printf("Yes\n");else printf("No\n")
#define YN(ans) if(ans)printf("YES\n");else printf("NO\n")
#define vector2d(type,name,h,...) vector<vector<type>>name(h,vector<type>(__VA_ARGS__))
#define umap unordered_map
#define uset unordered_set
using namespace std;
using ll = long long;
const int MOD=1000000007;
//入力系
void scan(int& a){scanf("%d",&a);}
void scan(long long& a){scanf("%lld",&a);}
template<class T> void scan(T& a){cin>>a;}
template<class T> void scan(vector<T>& vec){for(auto&& it:vec)scan(it);}
void in(){}
template <class Head, class... Tail> void in(Head& head, Tail&... tail){scan(head);in(tail...);}
//出力系
void print(const int& a){printf("%d",a);}
void print(const long long& a){printf("%lld",a);}
void print(const double& a){printf("%.15lf",a);}
template<class T> void print(const T& a){cout<<a;}
template<class T> void print(const vector<T>& vec){if(vec.empty())return;print(vec[0]);for(auto it=vec.begin();++it!= vec.end();){putchar(' ');print(*it);}}
void out(){putchar('\n');}
template<class T> void out(const T& t){print(t);putchar('\n');}
template <class Head, class... Tail> void out(const Head& head,const Tail&... tail){print(head);putchar(' ');out(tail...);}
//デバッグ系
template<class T> void dprint(const T& a){cerr<<a;}
template<class T> void dprint(const vector<T>& vec){if(vec.empty())return;cerr<<vec[0];for(auto it=vec.begin();++it!= vec.end();){cerr<<" "<<*it;}}
void debug(){cerr<<endl;}
template<class T> void debug(const T& t){dprint(t);cerr<<endl;}
template <class Head, class... Tail> void debug(const Head& head, const Tail&... tail){dprint(head);cerr<<" ";debug(tail...);}

vector<ll> fibo(50,-1);
ll fibonacci(ll n){
    if(fibo[n]!=-1){
        return fibo[n];
    }else if(n==0){
        fibo[0]=1;
        return 1;
    }else if(n==1){
        fibo[1]=1;
        return 1;
    }else{
        fibo[n]=fibonacci(n-2)+fibonacci(n-1);
        return fibo[n];
    }
}

int main(){
    int n;
    in(n);
    out(fibonacci(n));
}

C++: #include<iostream>
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i,n) for(int i=0;i<n;i++)
using P = pair<int,int>;

/* 大文字を小文字に変換 */
char tolower(char c) {return (c + 0x20);}
/* 小文字を大文字に変換 */
char toupr(char c) {return (c - 0x20);}

// if('A'<=s[i] && s[i]<='Z') s[i] += 'a'-'A';

/*
string s = "abcdefg"
s.substr(4) "efg"
s.substr(0,3) "abc"
s.substr(2,4) "cdef"

// イテレータ要素のインデックス
distance(A.begin(), itr);
*/

const int MAX_N = 45;

int fib[MAX_N];
int n;

void init(){
    rep(i,MAX_N) fib[i] = -1;
}

int calc_fib(int _n){
    int fib1, fib2;
    if(fib[_n-1] != -1) fib1 = fib[_n-1];
    else fib1 = calc_fib(_n-1);
    if(fib[_n-2] != -1) fib2 = fib[_n-2];
    else fib2 = calc_fib(_n-2);
    return fib[_n] = fib1 + fib2;
}

int main()
{
    cin >> n;
    init();
    fib[0] = fib[1] = 1;
    cout << calc_fib(n) << endl;
}

C++: #include <bits/stdc++.h>
#define ALL(a)  (a).begin(),(a).end()
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<long long> vll;
typedef vector<vector<long long>> vvll;
template <typename T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template <typename T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const long long INF = 1LL << 60;

int main(){
  int n;
  cin >> n;
  vi fib(50, -1);
  fib.at(0) = 1;
  fib.at(1) = 1;

  for(int i = 2; i <= n; i++){
    fib.at(i) = fib.at(i-1) + fib.at(i-2);
  }
  cout << fib.at(n) << endl;
}

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

const int N = 102;

long m[N][N], p[N+1];

int matrixChainOrder(int n){

  for(int i=1; i<n; i++){ m[i][i] = 0; }

  for(int l=2; l<n; l++){
    for(int i=1; i < n - l + 1; i++){
      int j = i+l-1;
      m[i][j] = std::numeric_limits<long>::max();
      for(int k=i; k<=j-1; k++){
        m[i][j] = std::min(m[i][j], m[i][k] + m[k+1][j] + p[i-1]*p[k]*p[j]);
      }
    }
  }
  return m[1][n - 1];
}

int main(){
  int n ;
  std::cin >> n; //number of matrix

  for(int i=1; i<=n; i++){
    std::cin >> p[i-1] >> p[i];
  }
  // for (int i = 0; i <=n; ++i) std::cout << p[i] << std::endl;
  std::cout << matrixChainOrder(n + 1) << std::endl;

  return 0;
}

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

int n;
int dp[44];

int fibo(int i){
  if(dp[i] != 0) return dp[i];
  else if(i == 0 || i == 1) return 1;
  else{
    return dp[i] = fibo(i-1) + fibo(i-2);
  }
}

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

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

ll F[45];
ll fibonacci(ll n) {
  if(n < 2)
    return F[n] = 1;
  if(F[n])
    return F[n];
  return F[n] = fibonacci(n-1) + fibonacci(n-2);
}
int main() {
  ll n;
  cin >> n;
  cout << fibonacci(n) << endl;
}

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

int main(int argc,char* argv[]){
  int a=1,b=1,x,n;
  cin>>n;

  for(int i=2;i<=n;i++){
    x=a+b;
    a=b;
    b=x;
  }
  cout<<x<<endl;
  return 0;
}

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

int main(void) {
    cin >> num;
    int array[num] = {};
    array[0] = 1;
    array[1] = 1;
    for (int i= 2; i <= num; i++) {
        array[i] = array[i - 1] + array[i - 2];
    }
    cout << array[num] << endl;
}

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

#define MAX 50

int dp[MAX];

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

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

  cout << fib(n) << endl;

  return 0;
}

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

int main(){
	int fib[45];
	int n;

	cin >>n;

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

	if(n == 0)
		cout <<fib[0] <<endl;
	else if(n == 1)
		cout <<fib[1] <<endl;
	else{
		for(int i=2;i<=n;i++){
			fib[i] = fib[i-1] + fib[i-2];
		}
		cout <<fib[n] <<endl;
	}
	return 0;
}

C++: #inclue<stdio>
#include<stream>
using namespace std;

int fibo(int x) {
  int a;
  if ( x == 0 ) return 1;
  if ( x == 1 ) return 1;
  a = fibo(x-1) + fibo(x-2);
  return a;
}

int main() {
  int x, y;

  cin >> x;

  y = fibo(x);

  cout << y << endl;

  return 0;
}

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