import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		long m = sc.nextLong();
		long prepre = 1;
		long prev = 1;
	    TreeSet<Long> set = new TreeSet<>();
	    set.add(1L);
		for (int i = 3; i <= n; i++) {
		    long cur = prepre + prev;
		    prepre = prev;
		    prev = cur;
		    set.add(prev);
		}
		long value = prev - m;
		if (value < 0) {
		    System.out.println(-1);
		    return;
		}
		int count = 0;
		while (value > 0) {
		    value -= set.floor(value);
		    count++;
		}
		System.out.println(count);
	}
}