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

/**************************************************************
	Problem: 1238
	User: wuzhijing
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2072 kb
****************************************************************/