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<map>
#include<set>
#include<list>
#include<cmath>
#include<queue>
#include<stack>
#include<cstdio>
#include<string>
#include<vector>
#include<complex>
#include<cstdlib>
#include<cstring>
#include<climits>
#include<numeric>
#include<sstream>
#include<iostream>
#include<algorithm>
#include<functional>

#define MP make_pair
#define PB push_back
#define ALL(x) (x).begin(),(x).end()
#define REP(i,n) for(int i=0;i<(n);i++)
#define REP1(i,n) for(int i=1;i<(n);i++)
#define REP2(i,d,n) for(int i=(d);i<(n);i++)
#define RREP(i,n) for(int i=(n);i>=0;i--)
#define CLR(a)      memset((a),0,sizeof(a))
#define MCLR(a)     memset((a),-1,sizeof(a))
#define RANGE(x,y,maxX,maxY) (0 <= (x) && 0 <= (y) && (x) < (maxX) && (y) < (maxY))

using namespace std;

typedef long long LL;
typedef unsigned long long ULL;
typedef vector<int> VI;
typedef vector<VI > VVI;
typedef vector<string> VS;
typedef vector<LL> VLL;
typedef pair<int,int> PII;

const int INF = 0x3f3f3f3f;
const LL INFL = 0x3f3f3f3f3f3f3f3fLL;
const double EPS = 1e-9;

const int DX[]={1,0,-1,0},DY[]={0,-1,0,1};

#define max 44

int fib(int n){
	int i,dp[max]={1,1};
	for(i=2;i<=n;i++)
		dp[i]=dp[i-1]+dp[i-2];
	return dp[n];
}

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

C++: #include<iostream>
using namespace std;
  
typedef long long hyper;
  
hyper fib(int n)
{
    if(n < 2) return 1;
    if(n == 2) return 2;
    if(n == 3) return 3;
    return 3 * fib(n - 2) - fib(n - 4);
}
   
int main()
{
    int n;
    cin >> n;
    cout << fib(n) << endl;
    return 0;
}

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

int fib(int n,int F[]){
	if(n==0||n==1){
		return F[n]=1;
	}
        if(F[n]!=-1){
             return F[n];
        }
	return F[n]=fib(n-1) + fib(n-2);
}

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

C++: #include <cassert>
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <algorithm>
#include <bitset>
#include <complex>

#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#define rep(i,n) for(int i=0;i<(n); i++)


using namespace std;
int main(){
	cin.tie(0);
    ios::sync_with_stdio(0); //この2行はより速度を向上させる
	// 追加２, 以降 cin の入力元が 'input.txt' になる
	//提出時に消す！！
	//std::ifstream in("sample.txt");
	//std::cin.rdbuf(in.rdbuf());

	int n;
	cin>>n;
	int F[50];
	F[0]=F[1]=1;
	for(int i=2;i<=n;i++) F[i]=F[i-1]+F[i-2];

	cout << F[n] << endl;

	return 0;
}

C++: #include<iostream>
using namespace std;
int main(){
    int n;
    cin>>n;
    int d[45]={1,1};
    for(int i=2;i<=n;++i) d[i]=d[i-1]+d[i-2];
    cout<<d[n]<<endl;
}

C++: #include <algorithm>
#include <cmath>
#include <ctime>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <utility>
#include <vector>
#include <cstring>
#include <tuple>
#include <bitset>
#include <unordered_map>
using namespace std;
typedef long long ll;

int const SIZ = 50;
int fib[SIZ];

void prepare() {
    fib[0] = fib[1] = 1;
    for (int i=2; i<SIZ; ++i) {
        fib[i] = fib[i-1] + fib[i-2];
    }
}

int main() {
    ios::sync_with_stdio(false);

    prepare();

    int n;
    cin >> n;
    cout << fib[n] << endl;

    return 0;
}

C++: #include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <climits>
#include <cfloat>
#include <functional>
#include <cctype>

using namespace std;

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

int memo[45];

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

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

	cout << fib(n) << endl;
	return 0;

}

C++: /*
    フィボナッチ数列
    https://onlinejudge.u-aizu.ac.jp/courses/lesson/1/ALDS1/10/ALDS1_10_A
*/
#include <bits/stdc++.h>
#define ll long long int
using namespace std;

ll fibonacci(ll n) {
    if (n == 0 || n == 1)
        return 1;

    ll n1 = 1, n2 = 1, n3 = 0;
    n3 = n1 + n2;
    for (ll i = 0; i < n - 2; i++) {
        n1 = n2;
        n2 = n3;
        n3 = n1 + n2;
    }
    return n3;
}

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

    ll n;
    cin >> n;

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