#define _CRT_SECURE_NO_WARNINGS
#include <cstdio>
#include <cstring>
#include <cmath>
#include <vector>
#include <list>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <algorithm>
#include <iostream>
#include <sstream>
using namespace std;
typedef pair<int, int> P;
typedef long long int llint;
const int INF = 10000000;
const llint LINF = 100000000;

int main(){
	int n;
	llint ans[80];
	 ans[0] = 1;
	 ans[1] = 1;

	 cin >> n;

	 for (int i = 1; i < n; i++){
		 ans[i + 1] = ans[i] + ans[i - 1];

	 }
	 cout << ans[n];
	 
	 return 0;

}