백준 16953번 파이썬

import sys

N, M = map(int, sys.stdin.readline().split())

def solution(N, M):
    count = 0
    if N == M:
        return -1

    while M > N:
        if str(M)[-1] == "1":
            M = (M - 1) // 10

        elif M % 2 == 0:
            M = M // 2

        else:
            return -1

        count += 1

    if M < N:
        return -1

    return count + 1


print(solution(N, M))