// Given a file of n trades, describe a function that computes the top k most commonly traded stock tickers. Each trade has a ticker and a size, the rest of the information about the trade is irrelevant.
//Part 2: Instead of a file, the trades come in a stream. Describe two functions, one that is run when a new trade is added, and one that returns the top k most commonly traded stock tickers.
// Problem: Given a string that represents a number in one base, convert it into a string representing the same number in another base.