#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
#define MOD 1000003
#define INF 100000000
using namespace std;
typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PI;


LL m[64] = {};

bool d(int i, int n) {
	if (i == n) {
		return m[i];
	}
	else {
		m[i + 2] = m[i] + m[i + 1];
		i++;
		return d(i, n);
	}
}
int main() {
	int n;
	cin >> n;
	m[0] = 1;
	m[1] = 1;
	d(0, n);
	cout << m[n] << endl;
	return 0;
}