#include<bits/stdc++.h>
using namespace std;
int dfs(int x){
	if(x == 1 || x == 2) return 1;
	return dfs(x - 1) + dfs(x - 2);
}
int main(){
	int x;
	cin >> x;
	cout << dfs(x);
	return 0;
}

前三个对了