#include<iostream>
using namespace std;

int main()
{
	unsigned long long d[1000];
	d[0] = 0;
	d[1] = 1;

	unsigned long long x;


	cin >> x;

	if (x == 1)
		return 0;

	int i = 1;

	do
	{
		++i;
		d[i] = d[i - 1] + d[i - 2];
	} while (d[i]<x);
	cout << i - 1;

	return 0;
}