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

/**************************************************************
	Problem: 1238
	User: wuzihang
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2072 kb
****************************************************************/