Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func fib(n int) int {
	x, y := 1, 1
	for n > 0 {
		x, y = y, x+y
		n--
	}
	return x
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}
	fmt.Println(fib(n))
}

func nextText(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

func nextInt(sc *bufio.Scanner) (int, error) {
	return strconv.Atoi(nextText(sc))
}

C++: #include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using vi = vector<i64>;
using vvi = vector<vi>;
constexpr i64 MOD = 1e9 + 7;

template<int n>
struct mat {
    vvi d;

    mat() {
        d = vvi(n, vi(n));
    }

    mat(initializer_list<initializer_list<i64>> m) {
        for (auto a: m) {
            vi row(a.begin(), a.end());
            d.emplace_back(row);
        }
        assert(n == d.size());
        assert(n == d.front().size());
    };

    mat operator+(const mat rhs) {
        mat ret;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                ret.d[i][j] = d[i][j] + rhs.d[i][j];
            }
        }
        return ret;
    }

    mat operator-(const mat rhs) {
        mat ret;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                ret.d[i][j] = d[i][j] - rhs.d[i][j];
            }
        }
        return ret;
    }

    mat operator*(const mat rhs) {
        mat ret;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                for (int k = 0; k < n; k++) {
                    ret.d[i][j] += d[i][k] * rhs.d[k][j];
                }
            }
        }
        return ret;
    }

    mat operator*(const i64 k) {
        mat ret;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                ret.d[i][j] = d[i][j] * k;
            }
        }
        return ret;
    }

    static mat eye() {
        mat ret;
        for (int i = 0; i < n; i++) {
            ret.d[i][i] = 1;
        }
        return ret;
    }
};

template<int k>
mat<k> pow(mat<k> a, i64 n) {
    if (n == 0) {
        return mat<k>::eye();
    }
    if (n % 2 == 0) {
        mat<k> t = pow(a, n / 2);
        return t * t;
    }
    return a * pow(a, n - 1);
}

i64 fib(i64 n) {
    if (n <= 1) return n;
    mat<2> f{{1, 1}, {1, 0}};
    mat<2> res = pow(f, n - 2);
    return res.d[0][0] + res.d[0][1];
}

int main() {
    int n;
    cin >> n;
    cout << fib(n + 1) << endl;
}

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

int ans[100];

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

int main(){
    int n;
    cin >> n;
    for(int i = 0; i <= n; i++){
        ans[i] = fib(i);
    }
    cout << ans[n] << endl;
}

C++: #pragma GCC optimize("Ofast","unroll-loops")
#pragma comment(linker, "/stack:200000000")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include<bits/stdc++.h>
using namespace::std;
__attribute__((constructor))
void init(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	cout<<fixed<<setprecision(15);
}
auto call=[](auto f,auto... args){return f(f,args...);};
auto call_memo=[](auto f,auto&& memo,auto... args){
	auto g=[&memo,f](auto g,auto... args)->decltype(auto){
		if(memo.count(make_tuple(args...)))return memo[make_tuple(args...)];
        else return memo[make_tuple(args...)]=f(g,args...);
    };
	return call(g,args...);
};

int main(){
	int n;
	cin>>n;
	auto f=[&](auto f,int t)->int{
		return t>=2?f(f,t-1)+f(f,t-2):1;
	};
	cout<<call_memo(f,map<tuple<int>,int>(),n)<<endl;
}

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

vector<int> fibonatti;
int dp[10000];
int calc(int n){
  if(n <= 1) return 1;
  if(dp[n] != -1)return dp[n];
  fibonatti[n] = calc(n - 1) + calc(n - 2);
  return dp[n] = fibonatti[n];
}

int main(int argc, char *argv[]){
  int n;
  cin >> n;
  fibonatti.resize(n);
  fibonatti[0] = fibonatti[1] = 1;
  for (int i = 0; i <= n; i++) {
    dp[i] = -1;
  }
  dp[0] = dp[1] = 1;
  std::cout << calc(n) << std::endl;
  return 0;
}

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

int fib(int n, int FIB[]){
    if (FIB[n]) return FIB[n];
    return FIB[n] = fib(n - 1, FIB) + fib(n - 2, FIB);
}

int main(){
    int n;
    cin >> n;
    int FIB[n+1] = {};
    FIB[0] = 1;
    if (n > 0) FIB[1] = 1;
    cout << fib(n, FIB) << endl;

    return 0;
}

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

int fibo[50];
int rec(int i){
    if(i == 0 || i == 1) return 1;
    if(fibo[i] != -1) return fibo[i];
    
    int ret = 0;
    ret = rec(i-1) + rec(i-2);
    return fibo[i] = ret;
}

int main(void){
    // Your code here!
    int N;
    cin >> N;
    for(int i = 0; i < 50; i++) fibo[i] = -1;
    cout << rec(N) << endl;
}

C++: #include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define rep(i,n) for(int i=0;i<n;++i)

using namespace std;

typedef pair<int,int>P;

const int MAX_N = 100005;

ll n;
pair<P,P> PP[100];

pair<P,P> multiple(pair<P,P> A,pair<P,P> B)
{
	pair<P,P> C;
	P p = A.first,q = A.second;
	P r = B.first,s = B.second;
	C.first = P((p.first*r.first+p.second*s.first),(p.first*r.second+p.second*s.second));
	C.second = P((q.first*r.first+q.second*s.first),(q.first*r.second+q.second*s.second));
	return C;
}

int main()
{
	int cnt=0;
	scanf("%lld",&n);
	if(n==0){
		printf("1\n");
		return 0;
	}else if(n==1){
		printf("1\n");
		return 0;
	}
	n;
	ll buff = n;
	while(buff != 1){
		buff /= 2;
		cnt++;
	}
	PP[0].first = P(0,1);
	PP[0].second = P(1,1);
	rep(i,cnt){
		PP[i+1] = multiple(PP[i],PP[i]);
	}
	pair<P,P> res;
	res.first = P(1,0);
	res.second = P(0,1);
	rep(i,cnt+1){
		if(n & (1 << i)){
			res = multiple(res,PP[i]);
		}
	}
	printf("%d\n",res.second.second);
	return 0;
}

C++: #include <map>
#include <set>
#include <list>
#include <cmath>
#include <deque>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <complex>
#include <cstdlib>
#include <cstring>
#include <numeric>
#include <utility>
#include <iostream>
#include <algorithm>
#include <functional>
#include <unordered_map>
#include <unordered_set>

using namespace std;

#define ll long long
#define ull unsigned long long
#define INF (1 << 30)
#define LLINF (1LL << 62)
#define MOD7 1000000007
#define MOD9 1000000009
#define eps 1e-9
#define P pair<int, int>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pul pair<ull, ull>
#define all(a) (a).begin(), (a).end()
#define FOR(i,a,b) for (int i=(a);i<(b);++i)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);--i)
#define REP(i,n) for (int i=0;i<(n);++i)
#define RREP(i,n) for (int i=(n)-1;i>=0;--i)

void YES() { cout << "YES\n"; }
void NO() { cout << "NO\n"; }
void Yes() { cout << "Yes\n"; }
void No() { cout << "No\n"; }
void yes() { cout << "yes" << endl; }
void no() { cout << "no" << endl; }

template<class T>
T fibonacci(T n) {
	T first = 1, second = 0, ans;
	for (int i = 0; i < n; ++i) {
		if (i == 1)
			second = 1;
		ans = first + second;
		first = second;
		second = ans;
	}
	return ans;
}

int main() {
	int n;
	cin >> n;
	cout << fibonacci(n + 1) << endl;

	return 0;
}

C++: #include <iostream>
using namespace std;
int n,a[45];

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