n, m = map(int, input().split())
A = [1, 1]
for _ in range(n - 2):
    A.append(A[-1] + A[-2])

d = A[-1] - m
ans = 0
for i in range(n - 3, -1, -1):
    a = A[i]
    if d >= a:
        d -= a
        ans += 1
if d != 0:
    ans = -1
print(ans)