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++: /**
*    created: 12.05.2020 12:38:55
**/
#include <bits/stdc++.h>
#define int long long
const int INF = 1e18L + 5;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep2(i, s, n) for (int i = (s); i < (int)(n); i++)
using namespace std;

signed main() {

    cin.tie(0);
    ios_base::sync_with_stdio(false);

    int n; cin >> n;
    int f[50];
    f[0] = f[1] = 1;
    rep2(i,2,50) {
        f[i] = f[i-1] + f[i-2];
    }
    cout << f[n] << endl;


    return 0;
}

C++: #include <stdlib.h>
#include <stdio.h>

int fib(int n){
int i;
int a[25];
a[0]=a[1]=1;
for(i=2;i<=n;i++){
a[i]=a[i-1]+a[i-2];
   }
return a[n];
}

int main(){

int x,n;
scanf("%d",&n);
x=fib(n);
printf("%d",x);

return 0;
}

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

//#define int long long
typedef long long ll;

typedef unsigned long long ul;
typedef unsigned int ui;
const ll mod = 1000000007;
const ll INF = mod * mod;
const int INF_N = 1e+9;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
#define all(v) (v).begin(),(v).end()
typedef pair<ll, ll> LP;
typedef long double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-12;
const ld pi = acos(-1.0);
//typedef vector<vector<ll>> mat;
typedef vector<int> vec;

//繰り返し二乗法
ll mod_pow(ll a, ll n, ll m) {
	ll res = 1;
	while (n) {
		if (n & 1)res = res * a%m;
		a = a * a%m; n >>= 1;
	}
	return res;
}

struct modint {
	ll n;
	modint() :n(0) { ; }
	modint(ll m) :n(m) {
		if (n >= mod)n %= mod;
		else if (n < 0)n = (n%mod + mod) % mod;
	}
	operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
modint operator+=(modint &a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= mod; return a; }
modint operator-=(modint &a, modint b) { a.n -= b.n; if (a.n < 0)a.n += mod; return a; }
modint operator*=(modint &a, modint b) { a.n = ((ll)a.n*b.n) % mod; return a; }
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, int n) {
	if (n == 0)return modint(1);
	modint res = (a*a) ^ (n / 2);
	if (n % 2)res = res * a;
	return res;
}

//逆元(Eucledean algorithm)
ll inv(ll a, ll p) {
	return (a == 1 ? 1 : (1 - p * inv(p%a, a)) / a + p);
}
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }

const int max_n = 1 << 18;
modint fact[max_n], factinv[max_n];
void init_f() {
	fact[0] = modint(1);
	for (int i = 0; i < max_n - 1; i++) {
		fact[i + 1] = fact[i] * modint(i + 1);
	}
	factinv[max_n - 1] = modint(1) / fact[max_n - 1];
	for (int i = max_n - 2; i >= 0; i--) {
		factinv[i] = factinv[i + 1] * modint(i + 1);
	}
}
modint comb(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[b] * factinv[a - b];
}
using mP = pair<modint, modint>;

int dx[4] = { 0,1,0,-1 };
int dy[4] = { 1,0,-1,0 };


ll dp[50];

void solve() {
    int n; cin >> n;
    dp[0] = 1;
    dp[1] = 1;
    rep(i, n){
        dp[i+2] = dp[i+1] + dp[i];
    }

    cout << dp[n] << endl;
}

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  //cout << fixed << setprecision(10);
  //init_f();
  //init();
  //int t; cin >> t; rep(i, t)solve();
  solve();
//   stop
    return 0;
}

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

using namespace std;

#define FOR(i,k,n) for(int i = (k); i < (n); i++)
#define REP(i,n) FOR(i,0,n)
#define INF 114514810
#define ELEM(array) (sizeof (array)/sizeof *(array))
#define MAX_N 100
typedef unsigned int UINT;
typedef long long ll;

int fib[50];

int  fibfunc(int k)
{
	if (k==0||k==1)
	{
		return 1;
	}
	return fibfunc(k - 1) + fibfunc(k - 2);
}

int main()
{
	fib[1] = 1;
	fib[0] = 1;
	int n;
	cin >> n;

	
	cout << fibfunc(n) << endl;

	return 0;
}

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

using namespace std;

int dp[50];

void makeFib(int n) {
  dp[0] = 1;
  dp[1] = 1;
  for (int i = 2; i <= n; i++) {
    dp[i] = dp[i - 1] + dp[i - 2];
  }
}

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

  cout << dp[n] << endl;
  return 0;
}

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

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

int main()
{
    int n, ans = 1;
    scanf("%d", &n);

    int tmp0, tmp1 = 1;
    rep(i, n-1){
        tmp0 = tmp1;
        tmp1 = ans;
        ans = tmp0 + tmp1; 
    }
    printf("%d\n", ans);
    return 0;
}

C++: #include <iostream>
const int MAX_N = 50;
using namespace std;

int dp[MAX_N];

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

    dp[0] = dp[1] = 1;
    for (int i = 2; i <= n; i++) {
        dp[i] = dp[i-1] + dp[i-2];
    }

    cout << dp[n] << endl;
    return 0;
}

C++: #include <iostream>

using namespace std;

int F[50];

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

C++: #include<stdio.h>
int a[10000]={1,1};
int kaishi(int n){
    if(a[n])return a[n];
    a[n]=kaishi(n-1)+kaishi(n-2);
    return a[n];
}
int main(){
    int n;
    scanf("%d",&n);
    printf("%d\n",kaishi(n));
    return 0;
}

C++: #include "bits/stdc++.h"
using namespace std;
int d;
int dd[50];
int fib(int a){
	if(a==0||a==1)return dd[a]=1;
	if(dd[a])return dd[a];
	return fib(a-1)+fib(a-2);
}

int main() {
int c;
cin>>c;
cout<<fib(c)<<endl;
	return 0;
}

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

#define NIL -1
#define INF 1000000001

using namespace std;

int fib(int n,vector<int> &fib_array){
     if(n == 0 || n == 1) {
         fib_array[n] = 1;
         return 1;
     }
     else {
         if(fib_array[n-2] == 0) fib_array[n-2] = fib(n-2,fib_array);
         if(fib_array[n-1] == 0) fib_array[n-1] = fib(n-1,fib_array);
         return fib_array[n-1] + fib_array[n-2];
     }
}

int main(){
    int n;
    scanf("%d",&n);
    vector<int> fib_array(n,0);
    printf("%d\n",fib(n,fib_array));
    return 0;
}