#include <iostream>
using namespace std;



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

  cin >> nr2;

  nr0 = 1;
  nr1 = 1;



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

  }
    cout << n;

}