使用ruby和sinatra，以及Phony gem如何从电话号码中找到alpha2代码？

I have an international number as a string, so 81312345678 (Japan, Tokyo number) or 85212345678 (Hong Kong) and I need to isolate the country code, 81 in the case of Japan and 852 in the case of Hong Kong, in order to then identify the 2 letter alpha2 code of the country.I have an international number as a string, so