The novel “Gadsby” is over 50,000 words in length. While 50,000 words is not normally remarkable for a novel, it is in this case because none of the words in the book use the letter E. This is particularly noteworthy when one considers that E is the most common letter in English.

Write a program that reads a list of words from a file and determines what proportion of the words use each letter of the alphabet. Display this result for all 26 letters and include an additional message that identifies the letter that is used in the smallest proportion of the words. Your program should ignore any punctuation marks that are present in the file and it should treat uppercase and lowercase letters as equivalent.