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>

using namespace std;

typedef long long ll;

const ll LongINF=1e13+7;
const int INF=1e9+7;
const int dx[]={0,1,0,-1};
const int dy[]={1,0,-1,0};

template<class T> inline bool chmin(T& a, T b) {if (a > b) {a = b;return true;}return false;}
template<class T> inline bool chmax(T& a, T b) {if (a < b) {a = b;return true;}return false;}
template <class T, class Y>T GCD(T a, Y b){if(a<b){int c=a;a=b;b=c;}if (a % b == 0){return b;}return GCD(b, a % b);}
void clear(queue<pair<int, int>> &q){queue<pair<int, int>> empty;swap(q, empty);} //queueの中身の型は適時変更を忘れない

#define rep(i,n) for(int i=0;i<(n);i++)

vector<ll> memo;

int fib(int i){
    if(i==1)return 1;
    else if(i==0)return 0;

    if(memo[i]!=-1)return memo[i];

    return memo[i]=fib(i-1)+fib(i-2);
}

int main(){
    int N;
    cin>>N;
    memo.assign(N+2,-1);
    cout<<fib(N+1)<<endl;
    return 0;
}

//a=97,z=122

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

using namespace std;

#define loop(x, start, end) for(int x = start; x < end; x++)

void fib(vector<int> &dp, int n) {
    dp[0] = 1;
    dp[1] = 1;
    loop (i, 2, n+1) {
        dp[i] = dp[i-1] + dp[i-2];
    }
}


int main(void){
    int n;
    cin >> n;
    vector<int> dp(n+1);
    fib(dp, n);
    cout << dp[n] << endl;
}

C++: #include <iostream>
#include <iomanip>
#include <vector>
#include <set>
#include <string>
#include <queue>
#include <algorithm>
#include <map>
#include <cmath>
#include <list>
#include <stack>
#include <cstdio>
#include <cstdlib>
#include <cstring>

#define rep(i, n) for (int i = 0; i < n; i++)

using namespace std;

const int INF = 1 << 30;
const int MOD = 1000000007;
const int MAX = 100000;
const int N = 44;

int memo[N+1];

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

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

C++: #include <iostream>
using namespace std;
typedef long long ll;
#define int ll

int dp[45];

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

signed main(void) {
  int n;
  cin >> n;
  cout << fib(n) << endl;
  return 0;
}

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

#define N 45
int A[N];

int fibonacci(int i) {
    if (A[i] != -1) {
        return A[i];
    }

    if (i == 0 || i == 1) {
        return 1;
    }

    A[i] = fibonacci(i - 1) + fibonacci(i - 2);
    return A[i];
}

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

    for (int i = 0; i <= n; i++) {
        A[i] = -1;
    }

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

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

#define rep(i, n) REP(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define MSG(a) cout << #a << " " << a << endl;
#define REP(i, x, n) for (int i = x; i < n; i++)
#define OP(m) cout << m << endl
typedef long long ll;
typedef unsigned long long ull;

//メモ化再帰
int f[50];
int fib(int i)
{
    if (i == 0 || i == 1)
        return 1;

    if (f[i] != -1)
        return f[i];

    return f[i] = fib(i - 1) + fib(i - 2);
}

int main()
{
    rep(i, 50) f[i] = -1;
    int n;
    cin >> n;
    OP(fib(n));
}

C++: #include<iostream>

using namespace std;
int fib(int n);
int memo[45];
int main() {
  int n;

  //入力
  cin >> n;

  //出力
  cout << fib(n) << endl;

  return 0;
}

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

C++: #include <bits/stdc++.h>
using namespace std;
#define r(i,n) for(auto i=0;i<n;i++)
#define s(c) static_cast<int>((c).size())

int main(){
	int n;
	cin >> n;
	int64_t fib[n+1];
	fib[0] = fib[1] = 1;
	for(int i = 2; i <= n; i++){
		fib[i] = fib[i-1] + fib[i-2];
	}
	cout << fib[n] << endl;
}

C++: #include <iostream>
#include <algorithm>
#include <string>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <cstdio>
#include <cmath>
#define rep(i,a,b) for(int (i)=(a);i<(b);i++)
#define INF 100000000
#define MAX_N 1000000
using namespace std;

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

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

inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}

typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> P;
typedef tuple<int,int,int> tpl;

#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define SORT(c) sort((c).begin(),(c).end())
#define REVERSE(c) reverse((c).begin(),(c).end())
#define LB(a,x) lower_bound((a).begin(), (a).end(), x) - (a).begin()
#define UB(a,x) upper_bound((a).begin(), (a).end(), x) - (a).begin()

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)
#define RFOR(i,a,b) for(int i=(a)-1;i>=(b);--i)
#define RREP(i,n) RFOR(i,n,0)

#define en "\n"

const double EPS = 1e-9;
const double PI  = acos(-1.0);
const int INT_INF = 2147483647;
const long long LL_INF = 1LL<<60;
const long long MOD = 1000000007;

#define CLR(a) memset((a), 0, sizeof(a))

#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

int fib[50];

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

int main(void){
    int n; cin >> n;
    REP(i,50) fib[i] = -1;
    fib[0] = 1; fib[1] = 1;
    int ans = rec(n);
    cout << ans << en;
    return 0;
}