听说明明要去旅行，远在美国的Tim给他打来了跨洋电话，可是中间出了点儿小问题。到底发生了什么呢？
Tim: Hello. May I speak to Mingming please?
Philip: You must have dialed the wrong number. There is no Mingming here.
Tim: Is this four two one double six five four?
Philip: No. This is four two one double six four five.
Tim: Sorry to have bothered you.
Philip: That's all right.
所以，明明的电话号码是多少呢？请用数字写在下面。

4 2 1 6 6 5 4