Go: package main

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

const (
	initialBufSize = 100000
	maxBufSize     = 1000000
)

var sc *bufio.Scanner

func initScanner(r io.Reader) *bufio.Scanner {
	buf := make([]byte, initialBufSize)

	sc := bufio.NewScanner(r)
	sc.Buffer(buf, maxBufSize)
	sc.Split(bufio.ScanWords) // bufio.ScanLines
	return sc
}

func main() {
	sc = initScanner(os.Stdin)
	fmt.Println(resolve(parseProblem()))
}

func parseProblem() int {
	return scanInt(sc)
}

func resolve(n int) int {
	dp := make([]int, n+1)
	dp[0], dp[1] = 1, 1
	for i := 2; i <= n; i++ {
		dp[i] = dp[i-1] + dp[i-2]
	}
	return dp[n]
}

// snip-scan-funcs
func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	i, _ := strconv.Atoi(sc.Text())
	return int(i)
}
func scanString(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

C++: // http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_10_A

#include <iostream>
#include <iomanip>

#include <vector>
#include <string>
#include <iterator>
#include <algorithm>

typedef long long ll;
const long double PI = (acos(-1));
const long long MOD = 1000000007;
#define rep(i,n) REP(i,0,n)
#define REP(i,x,n) for(int i=x;i<n;++i)

using namespace std;

// change min/max
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; }

template<class T> void output(std::vector<T> & A) {
    const int n = A.size();
    for (int i = 0; i < n - 1; ++i) {
        std::cout << A[i] << " ";
    }
    std::cout << A[n - 1] << std::endl;
}


int fib(const int n, vector<int>& dp) {
    if (n == 0) return 1;
    if (n == 1) return 1;
    if (dp[n] != -1) return dp[n];
    dp[n] = fib(n - 1, dp) + fib(n - 2,dp);
    return dp[n];
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);
    std::cout << std::fixed << std::setprecision(15);

    const long maxn = 45;
    vector<int> dp(maxn, -1);
    dp[0] = dp[1] = 1;

    int n; cin >> n;
    const int ret = fib(n, dp);
    cout << ret << endl;

    return 0;
}