n,m=map(int,input().split())
ary=[1,1]
for _ in range(n-2):
  ary.append(ary[-1]+ary[-2])
cnt=0
for x in ary[::-1]:
  if ary[-1]-m>=x:
    m+=x
    cnt+=1
if ary[-1]==m:
  print(cnt)
else:
  print(-1)