Finding the most frequently occurring words in a text file

There is a file approximately 1 MB in size containing Russian text. The goal of the business task is to identify the top 3 or top 5 words with the highest frequency of occurrence. What steps and tools are required for a developer to create such functionality?

Input data: a text file (~1 MB) with regular Russian text. Required result: a list of the most frequently occurring words (top 3 / top 5).