import sys def get_jiaoji(q_1, q_2): j_ = [] if(q_1[1] >= q_2[0] and q_1[0] <= q_2[0] ): j_ = [q_2[0], min(q_1[1], q_2[1])] elif(q_2[1] >= q_1[0] and q_2[0] <= q_1[0]): j_ = [q_1[0], min(q_2[1], q_1[1])] else: j_ = [-10E-9, -10E-9] return j_ for line in sys.stdin: a = line.split() qujian_1 = [int(a[0]), int(a[1])] qujian_2 = [int(a[2]), int(a[3])] qujian_3 = [int(a[4]), int(a[5])] max_ans = -1000 jiaoji_1 = get_jiaoji(qujian_1, qujian_2) jiaoji_2 = get_jiaoji(qujian_2, qujian_3) jiaoji_3 = get_jiaoji(qujian_1, qujian_3) ans = 2 * max(jiaoji_1[-1], jiaoji_2[-1], jiaoji_3[-1]) if (ans < 0): ans = -1 print(ans)