n,m=map(int,input().split())
count=0
if n==2 and n<m:print(1)
else:
    while 1:
        count+=1
        if n<=m and n>2 and m>2:
            print(count)
            break
        a=n//2
        b=n-a
        if a%2 or b%2:
            print(-1)
            break
        n=a