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

#define _sel(_1, _2, x, ...) x
#define repn(i, n) for (ll i = 0; i < (n); i++)
#define reps(i, a, b) for (ll i = (a); i < (b); i++)
#define rep(i, ...) _sel(__VA_ARGS__, reps, repn)(i, __VA_ARGS__)
#define reppn(i, n) for (ll i = 1; i <= (n); i++)
#define repps(i, a, b) for (ll i = (a); i <= (b); i++)
#define repp(i, ...) _sel(__VA_ARGS__, repps, reppn)(i, __VA_ARGS__)
#define rrepn(i, n) for (ll i = (n) - 1; i >= 0; i--)
#define rreps(i, a, b) for (ll i = (b) - 1; i >= (a); i--)
#define rrep(i, ...) _sel(__VA_ARGS__, rreps, rrepn)(i, __VA_ARGS__)
#define rreppn(i, n) for (ll i = (n); i >= 1; i--)
#define rrepps(i, a, b) for (ll i = (b); i >= (a); i--)
#define rrepp(i, ...) _sel(__VA_ARGS__, rrepps, rreppn)(i, __VA_ARGS__)

#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
#define rng(v) (v).begin(), (v).end()
#define rrng(v) (v).rbegin(), (v).rend()
#define _shv(v) for (auto _t1 : v) cerr << _t1 << " "; cerr << endl;
#define dbg(x) cerr << #x << ": " << (x) << endl;
#define dbgv(v) cerr << #v << ": "; _shv(v);
#define dbgm(m) cerr << #m << ":" << endl; for (auto _t2 : m) { _shv(_t2); }

using namespace std;
using ll = long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;
using vb = vector<bool>;
using vc = vector<char>;
using vs = vector<string>;
using vpii = vector<pii>;
using vpll = vector<pll>;
using vvi = vector<vector<int>>;
using vvl = vector<vector<ll>>;
using vvb = vector<vector<bool>>;
using vvc = vector<vector<char>>;
using vvs = vector<vector<string>>;

const int INF = 1e9;
const ll LINF = 1e18;
const ll MOD = 1e9 + 7;
const int DX[4] = {1, 0, -1, 0};
const int DY[4] = {0, 1, 0, -1};

inline void yn(bool f) { cout << (f ? "Yes" : "No") << endl; }
template<typename T> inline void prt(T x) { cout << (x) << endl; }
template<typename T> inline void prtv(T& v) { for (auto t : v) cout << t << " "; cout << endl; }
template<typename T> inline void prtl(T& v) { for (auto t : v) cout << t << endl; }
template<typename T> inline T pop(stack<T>& x) { T t = x.top(); x.pop(); return t; }
template<typename T> inline T pop(queue<T>& x) { T t = x.front(); x.pop(); return t; }
template<typename T> inline T pop(priority_queue<T>& x) { T t = x.top(); x.pop(); return t; }
template<typename T> inline int sz(T& x) { return x.size(); }
template<typename T> inline ll pow2(T n) { return 1ll << n; }
template<typename T, typename U> inline int bit(T x, U n) { return x >> n & 1; }

template<typename T, typename U>
inline void getv(T& v, U n) { v = T(n); rep(i, n) cin >> v[i]; }
template<typename T, typename U>
inline void inv(T& v, U n) { v = T(n); rep(i, n) { cin >> v[i]; v[i]--; } }
template<typename T, typename U>
inline void getm(T& v, U r, U c) { v = T(r); rep(i, r) getv(v[i], c); }
template<typename T, typename U>
inline void inm(T& v, U r, U c) { v = T(r); rep(i, r) inv(v[i], c); }
template<typename T, typename U>
inline bool cmax(T& m, U x) { if (m < x) { m = x; return true; } return false; }
template<typename T, typename U>
inline bool cmin(T& m, U x) { if (m > x) { m = x; return true; } return false; }


int main() {
    int n;
    cin >> n;
    if (n <= 1) {
        prt(1);
        return 0;
    }
    vl f(n + 1, 1);
    repp(i, 2, n) {
        f[i] = f[i - 1] + f[i - 2];
    }
    prt(f[n]);

    return 0;
}

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

vector<int> dp;

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

int main(){
    int n; cin >> n;
    dp.assign(n+1,-1);
    dp[0]=1;
    dp[1]=1;
    cout << fib(n) << endl;
}
//g++ -o proa.exe proa.cpp

//VSCなら./test
//Atomならtest.exe

C++: #include <bits/stdc++.h>
#define lp(n) for(int i = 0; i < n; i++)
using namespace std;
int main(){
  int n;
  unsigned long long A[45];
  A[0] = 1;
  A[1] = 1;
  for(int i = 2; i <= 44; i++) A[i] = A[i-1] + A[i-2];
  cin >> n;
  cout << A[n] << endl;
  return 0;
}

C++: #include <cstdio>

int compute_fibonacci(int num)
{
    int prev_num = 1;
    int current_num = 1;
    for(int i = 2; i <= num; i++) {
        int tmp = current_num;
        current_num = current_num + prev_num;
        prev_num = tmp;
    }
    return current_num;
}

int main()
{
    int num;
    scanf("%d", &num);
    printf("%d\n", compute_fibonacci(num));
    return 0;
}

C++: #define PI 3.14159265359
#define INF 2000000000
#define MAX 500000
#include <map>
#include <algorithm>
#include <vector>
#include <queue>
#include <iostream>
#include <string>
#include <cstring>
#include <cmath>
#include <cstdio>
using namespace std;
typedef long long ll;

int main(){
    ll F[45]={0};
    int n;
    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;
}