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

	return 0;
}

/**************************************************************
	Problem: 1238
	User: zhuanghaoxiang
	Language: C++
	Result: Memory Limit Exceed
****************************************************************/