N, M = map(int, input().split())
fib = [0]*N
fib[0]=fib[1]=1
num = []
for i in range(2,N):
    fib[i] = fib[i-1]+fib[i-2]
    num.append(fib[i-2])
if fib[i]<M:
    print(-1)
else:
    ss = fib[i]-M
    res = 0
    while num:
        nn = num.pop()
        if ss>=nn:
            ss -= nn
            res += 1
    if ss==0:
        print(res)
    else:
        print(-1)