N, M = map(int, input().split())
F = [1] * N
for i in range(2, N):
    F[i] = F[i - 1] + F[i - 2]


if M > F[N - 1]:
    print(-1)
    exit()

ans = 0
now = F[N - 1] - M
for i in range(N - 1, -1, -1):
    if now >= F[i]:
        ans += 1
        now -= F[i]

print(ans)