#include <iostream>
using namespace std;



int main()
{
  unsigned long long int nr0 = 0, nr1 = 0, nr2 = 0, n = 0, X = 0, copienr2 = 0;

  cin >> nr2;

  nr0 = 1;
  nr1 = 1;


  if(nr2 >=2)
  {
        for(int i = 3; i<=nr2; i++)
  {
      copienr2 = nr1+nr0;
      nr0=nr1;
      nr1=copienr2;
        if(copienr2 < nr2)
            n=i;

  }
    cout << n;
  }else{

  if(nr2==0)
    cout << "0";
  else if(nr2==1)
    cout << "1";

  }





}