#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main() {
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	/*fstream cin("input.txt");
	ofstream cout("output.txt");*/
	vector<long long> v;
	v.push_back(0);
	v.push_back(1);
	while (v.back() < 1e18) {
		v.push_back(v[v.size() - 1] + v[v.size() - 2]);
	}
	long long n;
	cin >> n;
	for (int i = 0; i < v.size(); i++) {
		if (v[i] == n) {
			cout << i;
			return 0;
		}
	}
	cout << -1;
}