#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: jiangyuanfeng
	Language: C++
	Result: Accepted
	Time:14 ms
	Memory:2072 kb
****************************************************************/