import sys

N,M = map(int,input().split())
fib = [0] * N
fib[0] = fib[1] = 1
for i in range(2,N):
    fib[i] = fib[i-1] + fib[i-2]
dif = fib[N-1] - M
if dif < 0:
    print(-1)
    sys.exit()
ans = 0
for i in reversed(range(N-2)):
    if dif >= fib[i]:
        dif -= fib[i]
        ans += 1
    if dif == 0:
        break
print(ans)