import java.util.Scanner;
// 0 1 2 3 5 8 13 21 34 55 89 144  
public class prog{
	public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
		long N = scn.nextLong();
		long a = 0;
		long b = 1;
		long fibval = a;
		long counter = 0;
		while (true) {
			if (fibval >= N) {
				System.out.println(counter);
				break;
			}
			fibval = a + b;
			counter++;
			a = b;
			b = fibval;
		}
	}
}