n, m = map(int, input().split())

C = [0 for _ in range(n + 1)]
C[1] = C[2] = 1
for i in range(3, n + 1):
    C[i] = C[i - 1] + C[i - 2]

res = C[n] - m
ans = 0
for i in range(n - 2, 0, -1):
    if res >= C[i]:
        ans += 1
        res -= C[i]
if res == 0:
    print(ans)
else:
    print(-1)