import sys
input=lambda: sys.stdin.readline().rstrip()
n,m=map(int,input().split())
A=[1,1]
for i in range(n-2):
  A.append(A[-1]+A[-2])

import bisect
ans=0
nn=A[-1]
while nn-m>0:
  d=nn-m
  if d==1:
    m+=1
    ans+=1
    break
  else:
    m+=A[bisect.bisect_left(A,d)-1]
    ans+=1
if nn!=m:
  print(-1)
else:
  print(ans)