Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N := sc.nextInt()
	dp := make([]int, N+1)
	dp[0] = 1
	dp[1] = 1
	for i := 2; i <= N; i++ {
		dp[i] = dp[i-1] + dp[i-2]
	}

	fmt.Fprintln(wtr, dp[N])
	wtr.Flush()
}

C++: /*
    Author:zeke
    
    pass System Test!
    GET AC!!
*/
#include <iostream>
#include <queue>
#include <vector>
#include <iostream>
#include <vector>
#include <string>
#include <cassert>
#include <algorithm>
#include <functional>
#include <cmath>
#include <queue>
#include <set>
#include <stack>
#include <deque>
#include <map>
#include <iomanip>
#include <utility>
#include <stack>
using ll = long long;
using ld = long double;
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(), (x).end()
#define rep3(var, min, max) for (ll(var) = (min); (var) < (max); ++(var))
#define repi3(var, min, max) for (ll(var) = (max)-1; (var) + 1 > (min); --(var))
#define Mp(a, b) make_pair((a), (b))
#define F first
#define S second
#define Icin(s) \
    ll(s);      \
    cin >> (s);
#define Scin(s) \
    ll(s);      \
    cin >> (s);
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;
}
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef vector<V> VV;
typedef vector<P> VP;
ll MOD = 1e9 + 7;
ll INF = 1e18;

using matrix = vector<V>;
matrix power(const matrix &a, int n)
{
    int sz = a.size();
    matrix res(sz, V(sz));
    rep(i, sz)
    rep(j, sz)
    {
        if (i == j)
            res[i][j] = 1;
        else
            res[i][j] = 0;
    }
    matrix r = a;
    while (n > 0)
    {
        if (n & 1)
        {
            matrix tmp(sz, V(sz, 0));
            rep(i, sz)
            rep(j, sz) rep(k, sz)
            {
                tmp[i][j] += res[i][k] * r[k][j];
            }
            res = tmp;
        }
        matrix tmp(sz, V(sz, 0));
        rep(i, sz)
        rep(j, sz)rep(k, sz)
        {
            tmp[i][j] += r[i][k] * r[k][j];
        }
        r = tmp;
        n >>= 1;
    }
    return res;
}

int fib(int n)
{
    matrix a(2, V(2));
    a[0] = {1, 1};
    a[1] = {1, 0};
    a = power(a, n - 1);
    V start = {1, 1};
    V res(2, 0);
    rep(i, 2)
    rep(j, 2)
    {
        res[i] += a[i][j] * start[j];
    }
    return res[0];
}
int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    cout << fib(n) << endl;
}

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

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

int main() {
	int n;
	cin >> n;
	if (n == 0) cout << 1;
	else if (n == 1) cout << 1;
	else {
		vector<int> fib{ 1, 1, 2 };
		for (int i = 2; i < n; ++i) {
			for (int i = 0; i < 2; ++i) fib[i] = fib[i + 1];
			fib[2] = fib[0] + fib[1];
		}
		cout << fib[2];
	}
	cout << endl;
}

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

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

using namespace std;

static vector<int> M(44, 0);

static inline int fibonacci(int n) {
  if (n == 0 || n == 1) {
    return 1;
  } 

  if (M[n] != 0) {
    return M[n];
  } 
  M[n] = fibonacci(n - 2) + fibonacci(n - 1);
  return M[n];
}

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

C++: #include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
const int INF=INT_MAX,MOD=1e9+7;

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

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#define REP(i, n) for(int i = 0; i < n; i++)
#define REPR(i, n) for(int i = n; i >= 0; i--)
#define FOR(i, m, n) for(int i = m; i < n; i++)
#define INF 2e9
#define ALL(v) v.begin(), v.end()
using namespace std;
typedef long long ll;
int main(){
    int n;
    cin >> n;
    int fib[n+1];
    fib[0] = 1;
    fib[1] = 1;
    REP(i,n - 1){
        fib[i+2] = fib[i+1] + fib[i];
    }
    cout << fib[n] << endl;

}