Need XPath to select based on longitude and latitude

I'm writing an XPath for a JavaScript search for countries that reside in a certain area. The countries have latitude and longitude elements, respectively, in the format of 00 00 N.

If the search is, say, lat more than 50 00 N, and a long less than 20 00 N, how would I write the path for it?

ex: /countries/country/geo[???]/name

The fact that the lat/long is in a format of separated numbers and a letter confuses me.