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++: /**
 * @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;
};