#! 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

def rec(xs,i,d,p)
    n = xs.size - 1
    t = [[i,d,p]]
    r = []
    while !t.empty?
        i, d, p = t.pop
        if d == 0
            r << p
            next
        end
        next if i > n
        x, s = xs[i]
        if x > d
            t << [i+1,d,p]
            next
        end
        next if s < d
        t << [i + 1, d, p]
        t << [i + 1, d - x, p + 1]
    end
    r.empty? ? - 1 : r.min
end

def fibs(n)
    f = [1, 1]
    (2...n).each do |i|
        f << f[i - 1] + f[i - 2]
    end
    fs = [[1,1]]
    (1...f.size).each do |i|
        fs << [f[i], f[i] + fs[i-1][1]]
    end
    fs.reverse
end

def solve(n,m)
    f = fibs(n)
    rec(f[2..-1], 0, f[0][0] - m, 0)
end

p solve(N,M)