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 <bits/stdc++.h>
using namespace std;

#define ll long long
#define vvi vector<vector<int>>
#define vec vector
#define pq priority_queue
#define all(v) (v).begin(), (v).end()
#define uniqueV(x) sort(x.begin(), x.end()); x.erase(unique(x.begin(), x.end()), x.end());
#define rep(i, n) for (int (i) = (0); (i) < (n); ++(i))
#define repp(i, m, n) for (int (i) = (m); (i) < (n); ++(i))
#define debug(x) cerr << #x << ": " << x << endl;
#define debug2(x, y) cerr<<"("<<#x<<", "<<#y<<") = "<<"("<<x<<", "<<y<<")"<<endl;
#define debug3(x, y, z) cerr<<"("<<#x<<", "<<#y<<", "<<#z<<") = "<<"("<<x<<", "<<y<<", "<<z<<")"<<endl;
#define debugB(value, size) cerr<<#value<<": "<<bitset<size>(value) << endl;
#define line() cerr << "---------------" << endl;

const int dx[] = {1, -1, 0, 0};
const int dy[] = {0, 0, -1, 1};
const double PI = 3.14159265358979323846;

template<typename T>
void printA(vector<T> &printArray, char between = ' ') {
   int paSize = printArray.size();
   for (int i = 0; i < paSize; i++) { cerr << printArray[i] << between;}
   if (between != '\n') {cerr << endl;}
}

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

int fib[100];

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

ll f2(int n) {
   if (n == 1 || n == 2) return 1;
   return f2(n-1) + f2(n-2);
}

int main() {
   int n;
   cin >> n;
   cout << f(n) << endl;

   return 0;
}

C++: 

def main():
    n = int(input())
    dp = [0] * 100
    dp[0] = 1
    dp[1] = 1
    for i in range(2, len(dp)):
        dp[i] = dp[i - 1] + dp[i - 2]
    print(dp[n])


if __name__ == '__main__':
    main()

C++: #include <iostream>
int F[100]; // ???????????????
int main() 
{
int n;
F[0] = 1;
F[1] = 1;
for (int i=2; i<45; ++i) 
{ // ???????????????
F[i] = F[i-2]+F[i-1];
}
cin>>n;
cout<<F[n];
}

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

int main(){
  int n,F[50];
  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 <bits/stdc++.h>
using namespace std;
using ll=long long;

#define REP(i,m,n) for(int i=(int)(m);i<(int)(n);++i)
#define rep(i,n) REP(i,0,n)
#define RREP(i,m,n) for(int i=(int)(m);i>=(int)(n);--i)
#define debug(x) cout << #x << "=" << (x) << endl;

template<class T> inline bool chmin(T& a,T b){if(a>b){a=b;return true;}return false;}
template<class T> inline bool chmax(T& a,T b){if(a<b){a=b;return true;}return false;}
template<typename T> void fail(T v){cout << v << endl;exit(0);}
//template end

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

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  solve();
  return 0;
}

C++: #include <iostream>
#define NUM 44

using namespace std;

int main(){
    int n, fib[NUM];

    cin >> n;
    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;
vector <int> F(100,-1);
int fib(int n){
    if(n==0 || n==1){
        return F[n]=1;
    }
    if(F[n]!=-1){
        return F[n];
    }
    return F[n]=fib(n-2)+fib(n-1);
}
int main() {
	int n;
	cin>>n;
	int ans;
	ans=fib(n);
	cout<<ans<<'\n';
	return 0;
}

C++: #include <cstdint>

using namespace std;

#define MEMO_SIZE 44
int64_t memo[MEMO_SIZE];

void fib_init()
{
  for (uint32_t i = 0; i < MEMO_SIZE; i++) {
    memo[i] = -1;
  }
}

uint32_t fib(uint32_t i)
{
  if (i == 0) {
    return memo[0] = 1;
  } else if (i == 1) {
    return memo[1] = 1;
  } else {
    if (memo[i] != -1)
      return memo[i];
    else {
      return fib(i - 1) + fib(i - 2);
    }
  }
}

#include <iostream>

int32_t main()
{
  fib_init();
  uint32_t i;
  cin >> i;
  cout << fib(i) << endl;
  return 0;
}

C++: #include<iostream>
using namespace std;
int fib(int n)
{
    int F[50];
    if(n<=1) return 1;
    for(int i = 2 ; i <= n; i++)
    {
        F[i] = F[i-1] + F[i-2];
    }
    return F[n];
}

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

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

int dp[50];

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

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

C++: #include<iostream>
#include<algorithm>
#define Max 44
#define null (-1)
using namespace std;
int f[Max];
int fib(int a){
	if(a==0 || a==1)
	return f[a]=1;
	if(f[a]!=null)
	return f[a]; 
	return f[a]=fib(a-1)+fib(a-2);
	
}
main(){
	int n;
	cin>>n;
	for(int i=0;i<=n;i++)
	f[i]=null;
	cout<<fib(n)<<endl;
	return 0;
}

C++: object Main extends App {
  val fibs: Array[Option[Int]] = Array.fill(45)(None)
  val n: Int = io.StdIn.readInt()
  fibs(0) = Some(1); fibs(1) = Some(1)
  println(fib(n))

  def fib(n: Int): Int = fibs(n) match {
    case None =>
      val fibN: Int = fib(n-1) + fib(n-2)
      fibs(n) = Some(fibN)
      fibN
    case Some(x) => x
  }
}

C++: #include <bits/stdc++.h>
#define LOOP(n) for (int _i = 0; _i < (n); _i++)
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define RREP(i, n) for (int i = (n); i >= 0; --i)
#define FOR(i, r, n) for (int i = (r); i < (n); ++i)
#define ALL(obj) begin(obj), end(obj)
using namespace std;
using ll = long long;
using ull = unsigned long long;
using P = pair<int, int>;
using Graph = vector<vector<int>>;

const int INF = 2100100100;
const int MOD = 1e9 + 7;

// 多次元 vector 生成
template <class T>
vector<T> make_vec(size_t a) {
    return vector<T>(a);
}
template <class T, class... Ts>
auto make_vec(size_t a, Ts... ts) {
    return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));
}
template <class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T &a, const T &b) {
    if (b < a) {
        a = b;
        return 1;
    }
    return 0;
}

int N, M, K, Q, W, H, R, C;
int dp[100];

ll f(int n) {
    if (n <= 1) return 1;
    if (dp[n] != INF) return dp[n];
    ll ret = f(n - 1) + f(n - 2);
    dp[n] = ret;
    return ret;
}

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

    cin >> N;
    REP(i, 100) dp[i] = INF;
    cout << f(N) << endl;
    return 0;
}

C++: // Ref : https://book.mynavi.jp/ec/products/detail/id=35408

#include <iostream>
using namespace std;

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

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

int main() {
  int fib[45];
  fib[0]=1;
  fib[1]=1;
  for(int i=2;i<45;i++){
    fib[i]=fib[i-1]+fib[i-2];
  }

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

  printf("%d\n",fib[n]);
}

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

int main(void)
{
    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;
}