Go: package main

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

var (
	nstr   func() string
	stdout *bufio.Writer
)

func init() {
	nstr = newReadString(os.Stdin)
	stdout = bufio.NewWriter(os.Stdout)
}

func main() {
	defer stdout.Flush()
	n := nint()
	r := fibonacci(n)
	fmt.Println(r)
}

func fibonacci(n int) int{
	if n == 0 || n == 1{
		return 1
	}else{
		fiList := make([]int, n+1)
		fiList[0] = 1
		fiList[1] = 1
		for i:=2; i<n+1; i++{
			fiList[i] = fiList[i-1] + fiList[i-2]
		}
		return fiList[n]

	}

}

func newReadString(ior io.Reader) func() string {
	r := bufio.NewScanner(ior)
	r.Buffer(make([]byte, 1024), int(1e+11))
	r.Split(bufio.ScanWords)

	return func() string {
		if !r.Scan() {
			panic("Scan failed")
		}
		return r.Text()
	}
}

func nint64() int64 {
	i, err := strconv.ParseInt(nstr(), 0, 64)
	if err != nil {
		panic(err.Error())
	}
	return i
}

func nint() int {
	return int(nint64())
}

func getIntSlice(n int) []int {
	b := make([]int, n)
	for i := 0; i < n; i++ {
		b[i] = nint()
	}
	return b
}

func getStringSlice(n int) []string {
	b := make([]string, n)
	for i := 0; i < n; i++ {
		b[i] = nstr()
	}
	return b
}

func gcd(x, y int) int {
	if y == 0 {
		return x
	}
	return gcd(y, x%y)
}

func lcm(x, y int) int {
	return x * y / gcd(x, y)
}

func contains(s []int, e int) bool {
	for _, a := range s {
		if a == e {
			return true
		}
	}
	return false
}

func bin(i int, prefix bool) string {
	i64 := int64(i)

	if prefix {
		return "0b" + strconv.FormatInt(i64, 2)
	} else {
		return strconv.FormatInt(i64, 2)
	}
}

func strReverse(s string) string {
	runes := []rune(s)
	for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
		runes[i], runes[j] = runes[j], runes[i]
	}

	return string(runes)
}

C++: #define _CRT_SECURE_NO_WARNINGS
#include "bits/stdc++.h"
//#include "libs.h"
#include <random>
#include <unordered_map>
#include <unordered_set>
//#include <opencv2/core.hpp>
//#include <opencv2/highgui.hpp>
//#include <opencv2/imgproc.hpp>

using namespace std;

//呪文
#define DUMPOUT cerr
#define dump(...) DUMPOUT<<"  ";DUMPOUT<<#__VA_ARGS__<<" :["<<__LINE__<<":"<<__FUNCTION__<<"]"<<endl;DUMPOUT<<"    ";dump_func(__VA_ARGS__)

typedef unsigned uint; typedef long long ll; typedef unsigned long long ull; typedef pair<int, int> pii; typedef pair<ll, ll> pll; typedef pair<double, double> pdd; typedef pair<string, string> pss;
template <typename _KTy, typename _Ty> ostream& operator << (ostream& o, const pair<_KTy, _Ty>& m) { o << "{" << m.first << ", " << m.second << "}"; return o; }
template <typename _KTy, typename _Ty> ostream& operator << (ostream& o, const map<_KTy, _Ty>& m) { if (m.empty()) { o << "{ }"; return o; } o << "{" << *m.begin(); for (auto itr = ++m.begin(); itr != m.end(); itr++) { o << ", " << *itr; } o << "}"; return o; }
template <typename _KTy, typename _Ty> ostream& operator << (ostream& o, const unordered_map<_KTy, _Ty>& m) { if (m.empty()) { o << "{ }"; return o; } o << "{" << *m.begin(); for (auto itr = ++m.begin(); itr != m.end(); itr++) { o << ", " << *itr; } o << "}"; return o; }
template <typename _Ty> ostream& operator << (ostream& o, const vector<_Ty>& v) { if (v.empty()) { o << "{ }"; return o; } o << "{" << v.front(); for (auto itr = ++v.begin(); itr != v.end(); itr++) { o << ", " << *itr; } o << "}"; return o; }
template <typename _Ty> ostream& operator << (ostream& o, const set<_Ty>& s) { if (s.empty()) { o << "{ }"; return o; } o << "{" << *(s.begin()); for (auto itr = ++s.begin(); itr != s.end(); itr++) { o << ", " << *itr; } o << "}"; return o; }
template <typename _Ty> ostream& operator << (ostream& o, const unordered_set<_Ty>& s) { if (s.empty()) { o << "{ }"; return o; } o << "{" << *(s.begin()); for (auto itr = ++s.begin(); itr != s.end(); itr++) { o << ", " << *itr; }	o << "}"; return o; }
template <typename _Ty> ostream& operator << (ostream& o, const stack<_Ty>& s) { if (s.empty()) { o << "{ }"; return o; } stack<_Ty> t(s); o << "{" << t.top(); t.pop(); while (!t.empty()) { o << ", " << t.top(); t.pop(); } o << "}";	return o; }
template <typename _Ty> ostream& operator << (ostream& o, const list<_Ty>& l) { if (l.empty()) { o << "{ }"; return o; } o << "{" << l.front(); for (auto itr = ++l.begin(); itr != l.end(); ++itr) { o << ", " << *itr; } o << "}"; return o; }
template <typename _KTy, typename _Ty> istream& operator >> (istream& is, pair<_KTy, _Ty>& m) { is >> m.first >> m.second; return is; }
template <typename _Ty> istream& operator >> (istream& is, vector<_Ty>& v) { for (size_t i = 0; i < v.size(); i++) is >> v[i]; return is; }
namespace aux { // print tuple
	template<typename Ty, unsigned N, unsigned L> struct tp { static void print(ostream& os, const Ty& v) { os << get<N>(v) << ", "; tp<Ty, N + 1, L>::print(os, v); } };
	template<typename Ty, unsigned N> struct tp<Ty, N, N> { static void print(ostream& os, const Ty& v) { os << get<N>(v); } };
}
template<typename... Tys> ostream& operator<<(ostream& os, const tuple<Tys...>& t) { os << "{"; aux::tp<tuple<Tys...>, 0, sizeof...(Tys)-1>::print(os, t); os << "}"; return os; }

template<typename A, size_t N, typename T> inline void Fill(A(&array)[N], const T &val) { std::fill((T*)array, (T*)(array + N), val); }

void dump_func() { DUMPOUT << endl; }
template <class Head, class... Tail> void dump_func(Head&& head, Tail&&... tail) { DUMPOUT << head; if (sizeof...(Tail) == 0) { DUMPOUT << " "; } else { DUMPOUT << ", "; } dump_func(std::move(tail)...); }

#define PI 3.14159265358979323846
#define EPS 1e-10
#define FOR(is,a,n) for(int is=(a);is<(n);++is)
#define REP(is,n)  FOR(is,0,n)
#define all(j) (j).begin(), (j).end()
#define SZ(j) ((int)(j).size())
#define fake false



unordered_map<ll, ll> memo;
ll fib(ll n) {
	if (memo.find(n) != memo.end())
		return memo[n];

	if (n <= 1)
		return memo[n] = 1;
	else
		return memo[n] = fib(n - 1) + fib(n - 2);
}

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

	ll n;
	cin >> n;
	cout << fib(n) << endl;

	return 0;
}

C++: #include<cstdio>

int main(){
    int a[44],n;
    a[0]=a[1]=1;
    for(int i=2;i<=44;i++) a[i]=a[i-1]+a[i-2];
    scanf("%d",&n);
    printf("%d\n",a[n]);
    return 0;
}

C++: #include<stdio.h>
#include<stream>
using namespace std;

int fibo(int x) {
  int a;
  if ( x == 0 ) return 1;
  if ( x == 1 ) return 1;
  a = fibo(x-1) + fibo(x-2);
  return a;
}

int main() {
  int x, y;

  cin >> x;

  y = fibo(x);

  cout << y << endl;

  return 0;
}

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

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

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

/*
long long fib(long long n){
    if(memo[n] != -1) return memo[n];
    else if(n == 0 || n == 1) return memo[n] = 1;
    else return memo[n] = fib(n - 1) + fib(n - 2);
}
*/

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

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

std::unordered_map<int, int> memo;

int fibonacci(int n) {
    if (memo.find(n) != memo.end()) {
        return memo[n];
    } else if (n == 0 || n == 1) {
        return 1;
    } else {
        int fib = fibonacci(n - 1) + fibonacci(n - 2);
        memo[n] = fib;
        return fib;
    }
}

int main() {
    int n;
    std::cin >> n;

    std::cout << fibonacci(n) << std::endl;
}

C++: #include<iostream>
using namespace std;
int dp[50];
int fib(int n) {
	if (n == 0 || n == 1)return dp[n] = 1;
	if (dp[n] != -1)return dp[n];
	return dp[n] = fib(n - 1) + fib(n - 2);
}
int main() {
	int n; cin >> n;
	for (int i = 0; i < 50; i++)dp[i] = -1;
	cout << fib(n) << endl;
	return 0;
}