#define _USE_MATH_DEFINES
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <cstring>
#include <queue>
#include <functional>
#include <set>
#include <map>
#include <string>
#include <cmath>
#include <math.h>
#include <complex>
#include <cassert>
#define rep(i,a,b) for (int i = (a); i < (b); i++)
#define case(i) cout<<"Case #"<<i<<": "
using namespace std;
typedef long long int ll;
typedef complex<double> com;
const int mod = 1e9 + 7;
const int MOD = 998244353;
const ll INF = 4e18;



int main() {
	int n; cin >> n;
	vector<ll> a(n + 1,0);
	a[0] = 1, a[1] = 1;
	rep(i, 0, n-1) {
		a[i + 2] = a[i] + a[i + 1];
	}
	cout << a[n] << endl;
	return 0;
}