#include<bits/stdc++.h>
using namespace std;
int d(int n){
	if(n==1||n==2) return 1;
	return d(n-1)+d(n-2);
}
int main(){
	int n;
	cin>>n;
	cout<<d(n);
	return 0;
}
/**************************************************************
	Problem: 1238
	User: houshanglin
	Language: C++
	Result: Accepted
	Time:14 ms
	Memory:2072 kb
****************************************************************/