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])

nn=A[-1]
ans=0
A=A[:n-2]
for a in A[::-1]:
  if a<=nn-m:
    m+=a
    ans+=1
if nn==m:
  print(ans)
else:
  print(-1)