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