#! ruby
# yukicoder My Practice
# author: Leonardone @ NEETSDKASU

def gs(); gets.chomp; end
def gi(); gets.to_i; end
def gss(); gets.chomp.split; end
def gis(); gss.map(&:to_i); end

N, M = gis

v = [0, 1, 1]

(3..N).each do |i|
    v << v[i - 1] + v[i - 2]
end

h = {0 => 0}

v.each do |x|
    t = h.dup
    h.each do |k,v|
        z = k + x
        if t.key? z
            t[z] = [t[z], v + 1].min
        else
            t[z] = v + 1
        end
    end
    h = t
end

ans = h[v[N] - M]

puts ans.nil? ? -1 : ans