N,M=map(int,input().split())
dp=[0]*N
dp[0]=1
dp[1]=1
for i in range(2,N):
    dp[i]=dp[i-1]+dp[i-2]
if M>dp[N-1]:
    print(-1)
    exit()
M=dp[N-1]-M
res=0
for i in reversed(range(N-2)):
    if M>=dp[i]:
        res+=1
        M-=dp[i]
print(res)