using System;

class MainClass {
  public static void Main (string[] args) {
    int r1 = 1, r2 = 1, z, a;
    a = int.Parse(Console.ReadLine());
    for (int i = 2; ; i++){
      if (a >= r1 && r2 > a){
        Console.WriteLine(i);
        break;
      }
    z = r2;
    r2 += r1;
    r1 = z;
    }
  }
}