// a dynamic programming approach for generating any number of fibonacci number
#include<bits/stdc++.h>
using namespace std;
 
long long int save[100]; // declare any sized array
long long int fibo(int n){
  if(n==0) return 0;
  if(n==1) return 1;
  if(save[n]!=-1) return save[n]; //if save[n] holds any value that means we have already calculated it and can return it to recursion tree
  save[n]=fibo(n-1)+fibo(n-2); // if it come tp this line that means I don't know what is the value of it
  return save[n];
}

int main(){
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  memset(save,-1,sizeof save);
  cout<<fibo(2)<<'\n';

  return 0;
}