Go: package main

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

// func fib(n int) int{
// 	if n == 0 || n == 1{
// 		return 1
// 	} else {
// 		return fib(n-1) + fib(n-2)
// 	}
// }

// func main(){
// 	sc := bufio.NewScanner(os.Stdin)
// 	sc.Scan()
// 	n, _ := strconv.Atoi(sc.Text())
// 	fmt.Println(fib(n))
// }

import (
	"fmt"
)

func main(){
	var n, pre1, pre2, now int
	fmt.Scan(&n)
	if n == 0 || n == 1{
		fmt.Println(1)
	} else {
		pre1, pre2 = 1, 1
		for i:=1; i<n; i++{
			now = pre1 + pre2
			pre2 = pre1
			pre1 = now
		}
		fmt.Println(now)
	}

}

C++: #include <cstdio>
#include <iostream>
#include <cmath>
#include <ctype.h>
#include <string>
#include <sstream>
#include <algorithm>
#include <cstdlib>
#include <map>
#include <queue>
#include <utility>
#include <vector>
#include <set>

using namespace std;

int main()
{
    int fib[45] = {};
    fib[0] = fib[1] = 1;

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

    return 0;
}

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

int main() {
	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;
}

C++: #include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cstring>
#include <queue>
#include <vector>
#include <functional>
#include <map>
#include <set>
#include <cmath>
#include <string>
#define SIZE 200005
#define INF 1000000005LL

using namespace std;
typedef long long int ll;
typedef pair <int,int> P;

int n;
ll K;

int main()
{
	scanf("%d",&n);
	int dp[50];
	for(int i=0;i<=n;i++){
		if(i==0||i==1){
			dp[i]=1;continue;
		}
		dp[i] = dp[i-1]+dp[i-2];
	}
	printf("%d\n",dp[n]);
	return 0;
}

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

int memo[111]={0};

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

int main(){
  int a;

  scanf(" %d",&a);

  fib(a);

  cout << memo[a] << endl;

  return 0;

}

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

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

C++: #include <iostream>
#include <cstring>
#define Max 100
using namespace std;
int dp[Max];
int fib(int n){
    if(n==0 || n==1)
        return 1;
    if(dp[n]>0)
        return dp[n];
    else{
        dp[n]=fib(n-1)+fib(n-2);
        return dp[n];
    }
    
}

int main()
{
    int n;
    cin>>n;
    memset(dp,0,100);
    cout<<fib(n)<<endl;
    return 0;
}

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



using namespace std;

int main() {
   

    long long n;
    cin >> n;
    long long 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-1] << endl;


}

C++: #include <iostream>
using namespace	std;
int main(){

  int n,a[45],i;

  cin>>n;
  a[0]=1;
  a[1]=1;

  for(i=2;i<=n;i++) a[i]=a[i-2]+a[i-1];

  cout<<a[n]<<endl;

  return 0;

}

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

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


}

C++: // ALDS1_10_A.cpp
// Dynamic Programming - Fibonacci Number

#include <iostream>
using namespace std;

int fib(int n) {
    if (n == 0 || n == 1)
        return 1;
    int pre = 1;
    int curr = 1;
    int next = 1;
    while (n-- > 1) {
        next = pre + curr;
        pre = curr;
        curr = next;
    }
    return next;
}

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

C++: #include <iostream>

using namespace std;

#define INF -1

int dp[45];

int main()
{
	for(int i = 0; i < 45; i++) { dp[i] = INF; }

	int n;

	cin >> n;

	dp[0] = 1;
	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<bits/stdc++.h>
using namespace std;
int main(){
  int n,d[50];
  d[0]=d[1]=1;
  for(int i=0;i<43;i++)d[i+2]=d[i]+d[i+1];
  cin>>n;
  cout<<d[n]<<endl;
  return 0;
}

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

#define rep(i, m, n) for(int(i) = (int)(m); i < (int)(n); ++i)
#define rep2(i, m, n) for(int(i) = (int)(n)-1; i >= (int)(m); --i)
#define REP(i, n) rep(i, 0, n)
#define REP2(i, n) rep2(i, 0, n)
#define all(hoge) (hoge).begin(), (hoge).end()
#define en '\n'
using ll = long long;
using ull = unsigned long long;
using ld = long double;
template <class T>
using vec = vector<T>;
template <class T>
using vvec = vector<vec<T>>;
typedef pair<ll, ll> P;
constexpr long long INF = 1LL << 60;
constexpr int INF_INT = 1 << 25;
constexpr long long MOD = (ll)1e9 + 7;
//constexpr long long MOD = 998244353LL;
using ld = long double;
static const ld pi = 3.141592653589793L;
typedef vector<ll> Array;
typedef vector<Array> Matrix;

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;
}

struct Edge {
    ll to, rev;
    long double cap;
    Edge(ll _to, long double _cap, ll _rev) {
        to = _to;
        cap = _cap;
        rev = _rev;
    }
};
using Edges = vector<Edge>;
using Graph = vector<Edges>;

void add_edge(Graph &G, ll from, ll to, long double cap, bool revFlag,
              long double revCap) {
    G[from].push_back(Edge(to, cap, (ll)G[to].size()));
    if(revFlag)
        G[to].push_back(Edge(from, revCap, (ll)G[from].size() - 1));
}

ll dp[50];

ll f(ll x) {
    if(x < 2)
        return 1;
    if(dp[x])
        return dp[x];
    return dp[x] = f(x - 1) + f(x - 2);
}

void solve() {
    ll n;
    cin >> n;
    cout << f(n) << en;
}

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

    solve();

    /*
    ll t;
    cin >> t;
    REP(i, t) { solve();}
    */

    return 0;
}

C++: #include <cstdio>
#include <vector>
using namespace std;

int main() {
	int n;
	int i;
	vector<long long> fib;
	scanf("%d",&n);
	fib.resize(n);
	fib[0]=fib[1]=1;
	for(i=2; i<n; ++i) {
		fib[i]=fib[i-1]+fib[i-2];
	}
	printf("%lld\n",fib[n-1]);
	return 0;
}

C++: #include<iostream>
#define MAX 45
using namespace std;

void Fibonachi(int F[], int n) {
	F[0] = F[1] = 1;
	for (int i = 2; i <= n; i++) {
		F[i] = F[i - 2] + F[i - 1];
	}
}

int main() {
	int n,F[MAX];
	cin >> n;
	Fibonachi(F,n);
	cout << F[n] << endl;
	return 0;
}

C++: #include<cstdio>
#include<iostream>
#include<algorithm>
#include<vector>
#include<set>
#include<functional>
#include<queue>
#include<math.h>
#define INF 999999

using namespace std;

int memo[50];

int fib(int n)
{
	memo[0] = 1;
	memo[1] = 1;

	if (n == 0)return 1;
	else if (n == 1)return 1;
	else {
		for (int i = 2; i <= n; i++) {
			memo[i] = memo[i - 1] + memo[i - 2];
		}
		return memo[n];
	}
}

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

	int ans = fib(n);
	cout << ans << endl;

	return 0;
}