[백준][Python] 16953번 A -> B

a,b = input().split()
a = int(a)
count = 0
while int(b) > a:
    
    if b[-1] == "1":
        b = b[:-1]
        count += 1
        
    elif int(b) % 2 ==0:
        b = int(b) // 2
        count += 1
        b = str(b)
    else:
        break

if int(b) == a:
    print(count+1)
else :
    print(-1)