n, m = map(int, raw_input().split())

a = [0]*(n+1)
a[1] = a[2] = 1
for i in xrange(2,n+1):
    a[i] = a[i-1] + a[i-2]

k = a[n] - m

ans = 0
for i in xrange(n-2,0,-1):
    if k >= a[i]:
        k -= a[i]
        ans += 1
print -1 if k else ans