Go: package main

/*
フィボナッチ数列
*/

import (
	"bufio"
	"bytes"
	"fmt"
	"log"
	"os"
	"strconv"
	"strings"
)

func fibWithMemo(n int, memo map[int]int) int {
	if n == 0 || n == 1 {
		return 1
	}
	if val, ok := memo[n]; ok {
		return val
	}
	memo[n] = fibWithMemo(n-1, memo) + fibWithMemo(n-2, memo)
	return memo[n]
}

func fib(n int) int {
	memo := make(map[int]int)
	return fibWithMemo(n, memo)
}

func main() {
	scanner := makeScanner(1024)
	n := eGetInt(scanner)
	fmt.Println(fib(n))
}

////////////////////////////////////////////////////////////////////////////////
// ライブラリ
////////////////////////////////////////////////////////////////////////////////
func makeScanner(maxByte int) *bufio.Scanner {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Buffer(make([]uint8, 0, 8192), maxByte)
	return scanner
}
func makeWordScanner() *bufio.Scanner {
	scanner := makeScanner(8192)
	scanner.Split(bufio.ScanWords)
	return scanner
}
func eGetLine(r *bufio.Scanner) string {
	if r.Scan() {
		return r.Text()
	}
	err := r.Err()
	if err != nil {
		log.Fatal(err)
	}
	// EOF
	return ""
}
func eGetInt(r *bufio.Scanner) int {
	line := eGetLine(r)
	return eAtoi(line)
}
func eGetFields(r *bufio.Scanner) []string {
	line := eGetLine(r)
	return strings.Fields(line)
}
func eGetInts(r *bufio.Scanner) []int {
	fields := eGetFields(r)
	ints := make([]int, len(fields))
	for i := 0; i < len(ints); i++ {
		ints[i] = eAtoi(fields[i])
	}
	return ints
}
func eGetChars(r *bufio.Scanner) []string {
	line := eGetLine(r)
	return strings.Split(line, "")
}
func eAtoi(s string) int {
	n, err := strconv.Atoi(s)
	if err != nil {
		log.Fatal(err)
	}
	return n
}

type ints []int

func (s ints) String() string {
	var buf bytes.Buffer
	buf.WriteString("[")
	sep := ""
	for _, v := range s {
		buf.WriteString(fmt.Sprintf("%s%d", sep, v))
		sep = ", "
	}
	buf.WriteString("]")
	return buf.String()
}

func reverse(a ints) ints {
	r := make(ints, len(a))
	for i := 0; i < len(a); i++ {
		r[i] = a[len(a)-1-i]
	}
	return r
}
func max(a ints) (int, bool) {
	if len(a) == 0 {
		return 0, false
	}
	m := a[0]
	for _, e := range a {
		if e > m {
			m = e
		}
	}
	return m, true
}
func min(a []int) int {
	m := a[0]
	for _, v := range a {
		if v < m {
			m = v
		}
	}
	return m
}

func sum(a ints) int {
	if len(a) == 0 {
		return 0
	}
	sum := 0
	for _, e := range a {
		sum += e
	}
	return sum
}
func find(n int, a ints) int {
	for i, v := range a {
		if n == v {
			return i
		}
	}
	return -1
}

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

typedef long long ll;

ll table[45];
bool flg[45];

ll fib(int n){
    if(flg[n])return table[n];
    else{
        flg[n]=true;
        return table[n]=fib(n-1)+fib(n-2);
    }
}


int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    table[0]=table[1]=1;
    flg[0]=flg[1]=true;
    int n;
    cin >> n;
    cout << fib(n) << endl;
}

C++: #include <bits/stdc++.h>
using namespace std;
//using ll = long long;
#define MAX 100

int main(void) {
  int n;
  cin >> n;
  
  vector<int> F(50);
  F.at(0) = F.at(1) = 1;
  for (int i = 2; i <= n; i++) F.at(i) = F.at(i-1) + F.at(i-2);

  cout << F.at(n) << endl;


}

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;
}