Go: package main

import "fmt"

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

	x, y := int64(0), int64(1)
	for i := 0; i < n; i++ {
		x, y = y, x+y
	}

	fmt.Println(x)
}

C++: #include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll INF = 1e18;
const ll mod = 1000000007;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
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 (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
int ctoi(char c) {
  if (c >= '0' && c <= '9') {
    return c - '0';
  }
  return 0;
}
ll factorial(ll n) {
  if (n == 1) {
    return 1;
  }
  ll ans = factorial(n-1);
  return ans*n;
}
ll gcd(ll a, ll b) {
  if (a < b) {
    ll tmp = a;
    a = b;
    b = tmp;
  }
  ll r = a%b;
  while(r != 0) {
    a = b;
    b = r;
    r = a%b;
  }
  return b;
}
ll lcm(ll a, ll b) {
  return (a/gcd(a, b))*b;
}

vector <ll> dp(50, -1);

ll fib(ll n) {
  if (n==0 || n==1) {
    dp.at(n) = 1;
    return dp.at(n);
  }
  if (dp.at(n) != -1) {
    return dp.at(n);
  }
  dp.at(n) = fib(n-1) + fib(n-2);
  return dp.at(n);
}

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

C++: #include <iostream>

using namespace std;

int temp_data[50];

int fib(int n) {
	if (temp_data[n] != -1) return temp_data[n];
	if (n == 0) return 1;
	if (n == 1) return 1;
	int res = fib(n - 1) + fib(n - 2);
	temp_data[n] = res;
	return res;
}

int main() {
	for (int i = 0; i < 50; i++) temp_data[i] = -1;

	int n;
	cin >> n;
	cout << fib(n) << endl;

	return 0;
}

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

C++: #include<iostream>
#include<algorithm>
#include<vector>
#include<stdio.h>
#include<cstring>
#include<math.h>
#include<map>
#include<bitset>
#include<iomanip>
#include<queue>
using namespace std;

#define rep(i, n) for (int i = 0; i < (int)(n); ++i)

int main() {
  int fib[44];
  int n;
  cin >> n;
  rep(i, n+1) {
    if(i == 0 || i == 1) {
      fib[i] = 1;
      continue;
    }
    fib[i] = fib[i-1] + fib[i-2];
  }
  cout << fib[n] << endl;
  return 0;
}

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

using namespace std;

#define FOR(i,s,e) for((i)=(s);(i)<(int)(e);(i)++)
#define REP(i,e) FOR(i,0,e)

#define all(o) (o).begin(), (o).end()
#define psb(x) push_back(x)
#define mp(x,y) make_pair((x),(y))

typedef long long ll;
typedef pair<int, int> PII;

const double EPS = 1e-10;

const int M = 2;
int a[M][M], b[M][M], w[M][M];
int n;

void multiple_mat_ab_b() {
  int i, j, k;
  memset(w, 0, sizeof(w));
  for (i=0; i<M; i++)
    for (j=0; j<M; j++)
      for (k=0; k<M; k++)
        w[i][j] += a[i][k]*b[k][j];

  for (i=0; i<M; i++)
    for (j=0; j<M; j++)
        b[i][j] = w[i][j];
}

void multiple_mat_aa_a() {
  int i, j, k;
  memset(w, 0, sizeof(w));
  for (i=0; i<M; i++)
    for (j=0; j<M; j++)
      for (k=0; k<M; k++)
        w[i][j] += a[i][k]*a[k][j];

  for (i=0; i<M; i++)
    for (j=0; j<M; j++)
        a[i][j] = w[i][j];
}

void pow_mat_a(int k) {
  a[0][0] = a[0][1] = a[1][0] = 1;
  a[1][1] = 0;

  b[0][0] = b[1][1] = 1;
  b[0][1] = b[1][0] = 0;

  //?????´???a???k????????????
  for (int i=0; i<k; i++)
    multiple_mat_ab_b();

}

int main() {
  scanf("%d ", &n);
  pow_mat_a(n);
  printf("%d\n", b[1][0]+b[1][1]);

	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
  
struct Node{
  int key;
  Node *right,*left,*p;
};
  
Node *NIL,*root;
  
void insert(int k){
  Node *x=root;
  Node *y=NIL;
  Node *T;
    
  T=(Node *)malloc(sizeof(Node));
  T->key=k;
  T->left=NIL;
  T->right=NIL;
    
  while(x!=NIL){
    y=x;
    if(T->key<x->key) x=x->left;
    else x=x->right;  
  }
  T->p=y;
  if(y==NIL) root=T;
  else if(T->key<y->key) y->left=T;
  else y->right=T;
}
  
void in(Node *T){
  if(T!=NIL){
    in(T->left);
    cout<<' '<<T->key;
    in(T->right);
  }
} 
 
void pre(Node *T){
  if(T!=NIL){
    cout<<' '<<T->key;
    pre(T->left);
    pre(T->right);
  }
}
  
int main(){
  int m,k;
  string str;
  cin>>m;
  for(int i=0;i<m;i++){
    cin>>str;
    if(str[0]=='i'){
      cin>>k;
      insert(k);
    }
    else {
      in(root);
      cout<<endl;
      pre(root);
      cout<<endl;
    }
  }
  return 0;
}

C++: def fib(n):
  if n <= 1:
      return n
  return fib(n - 1) + fib(n - 2)

n = int(strip(raw_input()))

print fib(n)

C++: #include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> P;

#define vi vector<int>
#define vl vector<long long>
#define REP(i, n) for (int i = 0; i < (int)(n); i++)
#define REPD(i, n) for (int i = (int)(n-1); i >= 0; i--)
#define FOR(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define FORD(i, a, b) for (int i = (int)(a); i >= (int)(b); i--)
#define INF 1e18
#define MOD 1e9+7

template<class T> bool chmax(T &a, const T & b) {
    if (a<b) {
        a = b;
        return true;
    }
    return false;
}

template<class T> bool chmin(T &a, const T & b) {
    if (a>b) {
        a = b;
        return true;
    }
    return false;
}

ll dp[50];

ll fib(int n) {
    if (dp[n] >= 0) return dp[n];
    if (n == 0) return dp[n] = 1;
    if (n == 1) return dp[n] = 1;
    return dp[n] = fib(n-1)+fib(n-2);
}

int main() {
    int n;
    cin >> n;
    REP(i, n+1) dp[i] = -1; 
    cout << fib(n) << endl;
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <map>
#include <numeric>
#include <string>
#include <cmath>
#include <iomanip>
#include <string>
#include <queue>
#include <list>
#include <stack>

typedef long long ll;
using namespace std;
const int mod = 1000000007;

vector<ll> f(45);

int main() {

    int n; cin >> n;

    f[0] = 1; f[1] = 1;

    for (int i = 2; i <= n; i++) {
        f[i] = f[i-1] + f[i-2];
    }

    cout << f[n] << '\n';

}

C++: #include <iostream>
#include <cmath>
#include <set>
#include <string>
#include <algorithm>
#include <vector>
#include <bitset>
#include <iomanip>
#include <map>

using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::vector;
using std::bitset;

#define rep(i,n)    for(int i=0; i<(int)n; i++)
typedef long double ld;
typedef long long ll;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef std::pair<int, int> pii;
typedef std::pair<ll, ll> pll;

template<class T>
using Graph = vector<vector<T>>;

void printFixedDouble(double d, int fix) {
    cout << std::fixed;
    cout << std::setprecision(fix) << d << endl;
}

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

    int fibonatti[45];

    fibonatti[0] = 1;
    fibonatti[1] = 1;
    for (int i = 2; i <= n; i++) {
        fibonatti[i] = fibonatti[i - 1] + fibonatti[i - 2];
    }

    cout << fibonatti[n] << endl;

}

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

using namespace std;

int fib[50];

int main()
{

    int n;

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

    cin>>n;

    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; cin >> n;
    int dp[50];
    dp[0] = 1; dp[1] = 1;
    for(int i = 0; i <= n; i++){
        if(i >= 2)dp[i] = dp[i - 1] + dp[i - 2];
    }
    cout << dp[n] << endl;
}

C++: #define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <iostream>
#include <cstdlib>
#include <string>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <random>
#include <map>

using namespace std;

int fibArray[50];

void makeFibArray() {
    for (int i = 2; i <= 46; i++) {
	fibArray[i] = fibArray[i - 1] + fibArray[i - 2];
    }
}

int main() {

    //cin.tie(0);
    //ios::sync_with_stdio(false);

    int n; scanf("%d", &n);
    fibArray[0] = 1;
    fibArray[1] = 1;
    makeFibArray();
    printf("%d", fibArray[n]);


    return 0;

}