x,y = map(int,input().split())
q = [(x,y,0)]
ans = 10
while q:
    x,y,c = q.pop()
    if x==y: ans = min(ans,c)
    if c >= 10: continue
    q.append((x+y,x-y,c+1))
    q.append((x+y,y-x,c+2))
print(ans if ans != 10 else -1)