we have to deal with variable length digit between first dash and last one,
here is an extreme example(normally is between 5 to 8 digits):
1-416-81-2878-3-4-5999-6-7.....8-9-9-789
the rule is:

before the second dash, it's area code,
and area code itself varies, for instance,
(US--1,UK---->44, HK--->512?)
after the last dash, it's extention number.

how to do?