#include <iostream>
#include <fstream>
using namespace std;

ifstream in("fibonacci.in");
ofstream out("fibonacci.out");

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

  in >> nr2;

  nr0 = 1;
  nr1 = 1;

int copienr2 = 0;
  for(int i = 3; i<=nr2; i++)
  {
      copienr2 = nr1+nr0;
      nr0=nr1;
      nr1=copienr2;
        if(copienr2 < nr2)
            n=i;

  }

  out << n;

}