#include<iostream>
using namespace std;

int main() {

  int n;
  cin>>n;

  int a[n+1];
  a[0] = 1;
  a[1] = 1;

  for(int i = 2; i <= n; i++) {
    a[i] = a[i-1] + a[i-2];
  }

  cout<<a[n]<<endl;
  
  return 0;
}

