Hi there,

I am **stuck** with a problem, and don't know where to start.

I am given a series of cities, and their locations in **longitude and latitude**. The goal is to find the two cities with the shortest distance.

I have an algorithm which, given the geographical locations (longitude and latitude) of two cities, **calculates the distance** between them in kilometres.

I also have an algorithm that can calculate the answer in nlogn time, but only with inputs of x,y coordinates, and NOT longitude / latutude :( ...

How could I **change longitude,latitude to x,y,** in order to use the algorithm and find the closest pairs?

Thank you!