#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <iomanip>
#include <cctype>
using namespace std;
typedef long long ll;

int main()
{
	int n;
	ll t[51] = {};
	t[0] = 1;
	t[1] = 1;
	for (int i = 2; i <= 50; i++)
	{
		t[i] = t[i - 1] + t[i - 2];
	}
	cin >> n;
	cout << t[n] << endl;
	return 0;
}