#!/usr/bin/ruby
n,m=gets.split.map(&:to_i)
fib=[0,1]
(2..n).each{|i|fib[i]=fib[i-1]+fib[i-2]}
target=fib[n]-m
r=0
n.downto(1){|i|
	if target>=fib[i]
		target-=fib[i]
		r+=1
	end
}
p target==0 ? r : -1