#yuki320
import sys

n,m=map(int,raw_input().split())
fib=[1,1]
for i in xrange(2,n+1):
 fib.append(fib[i-2]+fib[i-1])
if fib[n-1]<m:
 print -1
 sys.exit()
dif=fib[n-1]-m
res=0
for i in xrange(n-2):
 if fib[n-3-i]<=dif:
  dif-=fib[n-3-i]
  res+=1
if dif:
 res=-1
print res