#include<iostream>
#include<fstream>
using namespace std;
ifstream F("nunta.in");
ofstream G("nunta.out");


int nr1,nr2,copie;

int main()
{  int i,n;
 
     F>>n;
     nr1=0;
     nr2=1;
     for(i=1;i<=n;i++)
     {
      copie=nr1;
      nr1=nr2;
      nr2=nr2+copie;
     }
     G<<nr2;
     
  return 0;
  
}