Go: package main

/*
フィボナッチ数列
*/

import (
	"bufio"
	"bytes"
	"fmt"
	"log"
	"os"
	"strconv"
	"strings"
)

func fibWithMemo(n int, memo map[int]int) int {
	if n == 0 || n == 1 {
		return 1
	}
	if val, ok := memo[n]; ok {
		return val
	}
	memo[n] = fibWithMemo(n-1, memo) + fibWithMemo(n-2, memo)
	return memo[n]
}

func fib(n int) int {
	memo := make(map[int]int)
	return fibWithMemo(n, memo)
}

func main() {
	scanner := makeScanner(1024)
	n := eGetInt(scanner)
	fmt.Println(fib(n))
}

////////////////////////////////////////////////////////////////////////////////
// ライブラリ
////////////////////////////////////////////////////////////////////////////////
func makeScanner(maxByte int) *bufio.Scanner {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Buffer(make([]uint8, 0, 8192), maxByte)
	return scanner
}
func makeWordScanner() *bufio.Scanner {
	scanner := makeScanner(8192)
	scanner.Split(bufio.ScanWords)
	return scanner
}
func eGetLine(r *bufio.Scanner) string {
	if r.Scan() {
		return r.Text()
	}
	err := r.Err()
	if err != nil {
		log.Fatal(err)
	}
	// EOF
	return ""
}
func eGetInt(r *bufio.Scanner) int {
	line := eGetLine(r)
	return eAtoi(line)
}
func eGetFields(r *bufio.Scanner) []string {
	line := eGetLine(r)
	return strings.Fields(line)
}
func eGetInts(r *bufio.Scanner) []int {
	fields := eGetFields(r)
	ints := make([]int, len(fields))
	for i := 0; i < len(ints); i++ {
		ints[i] = eAtoi(fields[i])
	}
	return ints
}
func eGetChars(r *bufio.Scanner) []string {
	line := eGetLine(r)
	return strings.Split(line, "")
}
func eAtoi(s string) int {
	n, err := strconv.Atoi(s)
	if err != nil {
		log.Fatal(err)
	}
	return n
}

type ints []int

func (s ints) String() string {
	var buf bytes.Buffer
	buf.WriteString("[")
	sep := ""
	for _, v := range s {
		buf.WriteString(fmt.Sprintf("%s%d", sep, v))
		sep = ", "
	}
	buf.WriteString("]")
	return buf.String()
}

func reverse(a ints) ints {
	r := make(ints, len(a))
	for i := 0; i < len(a); i++ {
		r[i] = a[len(a)-1-i]
	}
	return r
}
func max(a ints) (int, bool) {
	if len(a) == 0 {
		return 0, false
	}
	m := a[0]
	for _, e := range a {
		if e > m {
			m = e
		}
	}
	return m, true
}
func min(a []int) int {
	m := a[0]
	for _, v := range a {
		if v < m {
			m = v
		}
	}
	return m
}

func sum(a ints) int {
	if len(a) == 0 {
		return 0
	}
	sum := 0
	for _, e := range a {
		sum += e
	}
	return sum
}
func find(n int, a ints) int {
	for i, v := range a {
		if n == v {
			return i
		}
	}
	return -1
}

C++: /**
 * @brief  : c++ code for AtCoder
 * @author : rk222
 * @created: 2020.03.09 01:35:30
 */

#define _CRT_SECURE_NO_WARNINGS
#include <algorithm>
#include <bitset>
#include <cmath>
#include <cstdio>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
using namespace std;

#define int long long

typedef long long ll;
typedef long double ld;
typedef pair<int, int> P;
typedef pair<int, P> P1;
typedef tuple<int, int, int> T;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<P> vp;
typedef vector<tuple<int, int, int>> vt;

#define fr first
#define sc second
#define mp make_pair
#define pb push_back
#define rep(i, x) for (int i = 0; i < x; i++)
#define rep1(i, x) for (int i = 1; i <= x; i++)
#define srep(i, s, x) for (int i = s; i < x; i++)
#define rrep(i, x) for (int i = x - 1; i >= 0; i--)
#define rrep1(i, x) for (int i = x; i > 0; i--)
#define rsrep(i, s, x) for (int i = x - 1; i >= s; i--)
#define maxs(x, y) (x = max(x, y))
#define mins(x, y) (x = min(x, y))
#define limit(x, l, r) max(l, min(x, r))
#define lims(x, l, r) (x = max(l, min(x, r)))
#define sor(v) sort(v.begin(), v.end())
#define rev(s) reverse(s.begin(), s.end())
#define lb(vec, a) lower_bound(vec.begin(), vec.end(), a)
#define ub(vec, a) upper_bound(vec.begin(), vec.end(), a)
#define uniq(vec) vec.erase(unique(vec.begin(), vec.end()), vec.end())
#define mp1(a, b, c) P1(a, P(b, c))
#define dame                                                                                  \
    puts("-1");                                                                               \
    return 0
#define yn                                                                                    \
    puts("Yes");                                                                              \
    else puts("No")
#define YN                                                                                    \
    puts("YES");                                                                              \
    else puts("NO")

template <typename A, typename B> string to_string(pair<A, B> p);
template <typename A, typename B, typename C> string to_string(tuple<A, B, C> p);
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);
string to_string(const string &s) {
    return '"' + s + '"';
}
string to_string(const char *s) {
    return to_string((string)s);
}
string to_string(bool b) {
    return (b ? "true" : "false");
}
string to_string(vector<bool> v) {
    bool first = true;
    string ret = "{";
    for (int i = 0; i < static_cast<int>(v.size()); i++) {
        if (!first) {
            ret += ", ";
        }
        first = false;
        ret += to_string(v[i]);
    }
    ret += "}";
    return ret;
}
template <size_t N> string to_string(bitset<N> v) {
    string ret = "";
    for (size_t i = 0; i < N; i++) {
        ret += static_cast<char>('0' + v[i]);
    }
    return ret;
}
template <typename A> string to_string(A v) {
    bool first = true;
    string ret = "{";
    for (const auto &x : v) {
        string s = to_string(x);
        if (!first) {
            ret += ", ";
        }
        if (s[0] == '{') {
            s = "\n" + s;
        }
        first = false;
        ret += s;
    }
    if (ret[ret.size() - 1] == '}') {
        ret += "\n}";
    } else {
        ret += "}";
    }
    return ret;
}
template <typename A, typename... Lest> string to_string(A *v, int n, Lest... L) {
    bool first = true;
    string ret = "{";
    rep(i, n) {
        auto x = v[i];
        string s = to_string(x, L...);
        if (!first) {
            ret += ", ";
        }
        if (s[0] == '{') {
            s = "\n" + s;
        }
        first = false;
        ret += s;
    }
    if (ret[ret.size() - 1] == '}') {
        ret += "\n}";
    } else {
        ret += "}";
    }
    return ret;
}
template <typename A, typename B> string to_string(pair<A, B> p) {
    return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
template <typename A, typename B, typename C> string to_string(tuple<A, B, C> p) {
    return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
           to_string(get<2>(p)) + ")";
}
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
    return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
           to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}
void name_disp(string s) {
    cerr << "-------" << endl;
    cerr << s << ": " << endl;
}
void val_disp() {
    cerr << endl;
}
template <typename First, typename... Lest> void val_disp(First F, Lest... L) {
    cerr << to_string(F) << endl;
    val_disp(L...);
}
template <typename A, typename... Lest> void val_disp(A *v, Lest... L) {
    cerr << to_string(v, L...) << endl;
    val_disp();
}
#define disp(...)                                                                             \
    name_disp(#__VA_ARGS__);                                                                  \
    val_disp(__VA_ARGS__)
#define adisp(a, ...)                                                                         \
    name_disp(#a);                                                                            \
    val_disp(a, __VA_ARGS__)

#ifdef int
const ll INF = 1002003004005006007ll;
#else
const int INF = 1002003004;
#endif

const int M = 100000000;
const int dir_4[4][2] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
const int dir_8[8][2] = {{1, 0}, {1, 1}, {0, 1}, {-1, 1}, {-1, 0}, {-1, -1}, {0, -1}, {1, -1}};

/* ------------------------------------- */

ll dp[100];

ll fib(ll n) {
    if (dp[n] > 0)
        return dp[n];

    dp[n] = fib(n - 1) + fib(n - 2);
    return dp[n];
}

signed main() {
    ll n;
    scanf("%lld", &n);
    rep(i, 100) {
        dp[i] = -1;
    }

    dp[0] = 1;
    dp[1] = 1;

    printf("%lld\n", fib(n));

    /* --------------------------------- */
    return 0;
};